Use of capsaicin receptor antagonists to treat symptoms of tear gas exposure

ABSTRACT

Disclosed are diaryl piperazines and related compounds. These compounds are selective modulators of capsaicin receptors, including human capsaicin receptors, that are, therefore, useful in the treatment of a chronic and acute pain conditions, itch and urinary incontinence. Methods of treatment of such disorders and well as packaged pharmaceutical compositions are also provided. Compounds of the invention are also useful as probes for the localization of capsaicin receptors and as standards in assays for capsaicin receptor binding and capsaicin receptor mediated cation conductance. Methods of using the compounds in receptor localization studies are given.

RELATED APPLICATION INFORMATION

This application claims the benefit of priority under 35 U.S.C. section 119(e) to Provisional Patent Applications 60/280,223, filed Mar. 30, 2001, 60/230,726, filed Sep. 7, 2000, and 60/219,529, filed Jul. 20, 2001. These applications are hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates compounds that bind with high selectivity and high affinity to Vanilloid Receptors, especially Type I Vanilloid Receptors, also known as capsaicin receptors or VR1 Receptors. In an important aspect the invention provides capsaicin receptor, preferably human VR1 receptor, antagonists that are not capsaicin analogs (e.g., they do not contain a phenyl ring with two oxygen atoms bound to two adjacent ring carbons), are free of agonist activity, and exhibit an unprecedented level of affinity for the VR1 receptor. In another aspect, the invention provides aryl piperazines and related compounds that act as VR1 receptor ligands. In addition, this invention relates to such VR1 receptor ligands, high affinity antagonists and pharmaceutical compositions comprising such compounds and to the use of such compounds in treatment of diseases and other health-related conditions. Additionally this invention relates to the use of aryl piperazines and related compounds as tool for the analysis of VR1 receptors and as probes for the quantitative measurement and localization of VR1 receptors in cell and tissue samples.

2. Background

The sensation of pain can be triggered by any number of physical or chemical stimuli. In mammals, the peripheral terminals of a group of specialized small diameter sensory neurons, termed “nociceptors” mediate this response to a potentially harmful stimulus.

In efforts to discover better analgesics for the treatment of both acute and chronic pain, and to develop treatments for various neuropathic pain states, considerable research has been focused on the molecular mechanism of nociception. The response to heat, low extracellular pH (acidity), or capsaicin (the compound responsible for the hotness of hot peppers) is characterized by the persistent activation of nociceptors. It has been shown that both heat and capsaicin are capable of activating dorsal root ganglion and trigeminal ganglion neurons via an influx of cations. Additionally, moderately acidic conditions produce this response and can also potentiate the response of nociceptors to heat and capsaicin.

Capsaicin responses in isolated sensory neurons show dose-dependence and are also evoked by structural analogues of capsaicin that share a common vanilloid moiety. The term vanilloid receptor (VR) was coined to describe the neuronal membrane recognition site for capsaicin and such related irritant compounds. It was postulated that the VR is a nonselective cation channel with a preference for calcium. In 1989, resiniteratoxin (RTX), a natural product of certain Euphorbia plants, was recognized as an ultrapotent VR agonist. Specific binding of 3 H RTX provided the first unequivocal proof for the existence of a vanilloid receptor. The capsaicin response is competitively inhibited (and thereby antagonized) by another capsaicin analog, capsazepine and is also inhibited by the non-selective cation channel blocker ruthenium red. These antagonists bind to VR with no more than moderate affinity (i.e., with K_(i) values of no lower than 140 uM).

Interest in characterizing VRs led to the cloning of a functional rat capsaicin receptor (VR1), from a rat dorsal root ganglion cDNA library. A human version of VR1 has also been described, and the term VR1 is used herein to refer to either or both.

The capsaicin receptor's channel opens in response to elevated temperatures (higher than about 45° C.). Capsaicin and related compounds, as well as protons are stimuli that lower the threshold channel opening, so that in the presence of any of these stimuli the capsaicin receptor can be opened even at room temperature.

Opening of the capsaicin receptor channel is followed by the release of inflammatory peptides from neurons expressing the receptor and other nearby neurons, increasing the pain response. After initial activation by capsaicin the capsaicin receptor undergoes a rapid desensitization, possibly via phosphorylation of intracellular sites of the receptor. Capsaicin and related VR1 agonist vanilloid compounds have enjoyed long pharmaceutical use as topical anesthetics. While such compounds initially cause a strong burning sensation, receptor desensitization provides pain relief.

Localization of the capsaicin receptor in the dorsal root ganglion established this receptor as a leading target for analgesic discovery. Most currently marketed analgesic compounds act centrally, and often have side effects. Analgesic compounds that act peripherally are desirable for treating acute and chronic pain more effectively and with fewer side effects. Thus, compounds that interact with the capsaicin receptors, particularly antagonists of this receptor, which would not elicit the initial painful sensation of currently marketed capsaicin containing compounds, are desirable for the treatment of chronic and acute pain, itch, and urinary incontinence.

3. Description of Related Art

The vanilloid compounds capsaicin and Resiniferatoxin (RTX) act as potent and specific agonists of the capsaicin receptor. Capsazepine (which contains a phenyl ring with two oxygen atoms bound to two adjacent ring carbons and is therefore a capsaicin analog) acts as a moderate affinity competitive capsaicin receptor antagonist. Iodo-RTX is a capsaicin analog that has recently been reported to act as a high affinity antagonist. The inorganic dye, Ruthenium red, also antagonizes capsaicin responses of the receptor, albeit as a non-selective cation channel blocker. For an extensive review of vanilloid receptor ligands see Szallasi and Blumberg, (Pharmacological Reviews (1999) 51(3): 159-211).

SUMMARY OF THE INVENTION

This invention relates to VR1 receptor ligands, particularly VR1 receptor antagonists, and methods of using VR1 receptor antagonists for the treatment of neuropathic pain, peripheral-nerve-mediated pain, and pain, inflammatory and broncho-constriction symptoms resulting from exposure to capsaicin-receptor-activating stimuli such as capsaicin and tear gas.

In one aspect the invention provides novel chemical compounds that act as capsaicin receptor modulatory agents, some of which exhibit antagonist potency greater than that of any previously described VR1 receptor antagonist. Compounds that act as capsaicin receptor antagonists and bind to capsaicin (preferably human VR1) receptors with K_(i) values of less than 100 uM, as measured by a capsaicin receptor binding assay, such as the assay given by Example 10, or that inhibit capsaicin activity in an assay for determination of capsaicin receptor antagonist effects (Example 11) with EC₅₀ values of less than or equal to 100 uM, are referred to herein as potent capsaicin receptor antagonists; such compounds that bind or antagonize with K₁ or EC₅₀ values of less than or equal to 10 uM are referred to herein as highly potent capsaicin receptor antagonists.

In an additional aspect, the invention provides methods of using the potent capsaicin receptor antagonist compounds of the invention for the treatment of symptoms resulting from exposure to painful capsaicin receptor activating stimuli. In particular, the invention provides methods of treating subjects who have been exposed to capsaicin or have been burnt by heat, light, tear gas, or acid exposure, the methods comprising administering to such subjects an effective amount of a potent capsaicin receptor antagonist, preferably a highly potent (high potency) capsaicin receptor antagonist, so that the subject's symptoms of pain or sensitivity are reduced. Preferred compounds of the invention provide pain relief without loss of consciousness, and preferably without sedation, in such subjects that is equal to or greater than the degree of pain relief that can be provided to such subjects by morphine without loss of consciousness. Highly preferred compounds provide such pain relief while causing only transient (i.e., lasting for no more than one half the time that pain relief lasts) or no sedation (see Example 16 for sedation assay). Subjects or patients referred to herein may be humans or non-human mammals including domestic companion animals (pets) and livestock animals, as discussed more fully below.

In yet another aspect the invention provides methods of treating of neuropathic pain based on the unexpected finding that capsaicin receptor antagonists can alleviate such pain.

This invention also provides aryl piperazines and related compounds that bind with high affinity and high selectivity to capsaicin receptors, including human capsaicin receptors, also known as VR1 receptors.

Thus, the invention provides novel compounds of Formula I, Formula II, Formula III, Formula IV, Formula V, Formula VI, or Formula VII, Formula VIII, Formula IX and Formulae A-F shown below (the “compounds of the invention,” hereinafter Formulae I-IX and Formulae A-F), and pharmaceutical compositions comprising compounds of Formulae I-IX and Formulae A-F.

The invention further comprises methods of treating patients suffering from certain diseases or conditions, especially those involving pain or urinary incontinence, with an amount of a compound Formulae I-IX and Formulae A-F that is effective to improve the symptoms (e.g., reduce pain or reduce the frequency of urinary incontinence) of the disease or condition being treated.

Additionally this invention relates to the use of the compounds of the invention as reagents, standards, and probes for measurement, characterization and localization of capsaicin receptors, particularly VR1 receptors (e.g., in cells or tissues.

Accordingly, a broad aspect of the invention is directed to compounds of Formula I:

or the pharmaceutically acceptable salts thereof, wherein:

-   A is chosen from O, S, NR_(A), CR_(B)R_(B)′, NR_(A)CR_(B)R_(B)′,     CR_(B)R_(B)′NR_(A), —CR_(A)═CR_(B)—, and C₃H₄; where R_(A), R_(B),     and R_(B)′ are independently selected at each occurrence from     hydrogen or alkyl; -   Z is oxygen or sulfur; -   R₁ and R₂ independently represent hydrogen or lower alkyl; or -   R₁ and R₂ are taken together to form a 5 to 8 membered nitrogen     containing ring of the formula:

wherein n is 1, 2, or 3;

-   R₃ and R₄ are independently selected at each occurrence from the     group consisting of hydrogen; halogen; hydroxy; amino; cyano; nitro;     —COOH; —CHO, optionally substituted alkyl; optionally substituted     alkenyl; optionally substituted alkynyl; optionally substituted     alkoxy; optionally substituted mono or dialkylamino; optionally     substituted alkylthio; optionally substituted alkyl ketone;     optionally substituted alkylester; optionally substituted     alkylsulfinyl; optionally substituted alkylsulfonyl; optionally     substituted mono- or di-alkylcarboxamide; optionally substituted     —S(O)_(n)NHalkyl; optionally substituted —S(O)_(n)N(alkyl)(alkyl);     optionally substituted —NHC(═O)alkyl; optionally substituted     —NC(═O)(alkyl)(alkyl); optionally substituted —NHS(O)_(n)alkyl;     optionally substituted —NS(O)_(n)(alkyl)(alkyl); optionally     substituted saturated or partially unsaturated heterocycloalkyl of     from 5 to 8 atoms, which saturated or partially unsaturated     heterocycloalkyl contains 1, 2, or 3 heteroatoms selected from N, O,     and S; optionally substituted aryl having from 1 to 3 rings; or     optionally substituted heteroaryl, said heteroaryl having from 1 to     3 rings, 5 to 8 ring members in each ring and, in at least one of     said rings, from 1 to about 3 heteroatoms per ring selected from the     group consisting of N, O, and S;     or any two -   R₃ and R₄ not attached to the same carbon may be joined to form an     optionally substituted aryl ring; a saturated or partially     unsaturated carbocyclic ring of from 5 to 8 members, which     carbocyclic ring is optionally substituted; or a saturated,     partially unsaturated, or aromatic heterocyclic ring of from 5 to 8     members, which heterocyclic ring is optionally substituted and     contains 1, 2, or 3 heteroatoms selected from N, O, and S; and -   Ar₁ and Ar₂ are the same or different and independently represent     optionally substituted cycloalkyl; an optionally substituted     heterocycloalkyl ring of from 5 to 8 atoms, which heterocycloalkyl     ring contains 1, 2, or 3 heteroatoms selected from N, Or and S;     optionally substituted aryl having from 1 to 3 rings; or optionally     substituted heteroaryl, said heteroaryl having from 1 to 3 rings, 5     to 8 ring members in each ring and, in at least one of said rings,     from X to about 3 heteroatoms per ring selected from the group     consisting of N, O, and S, and -   n is independently chosen at each occurrence from 0, 1, and 2.

In specific embodiments of the invention R₁ and R₂ are joined to form a 5 to 7-membered heterocycloalkyl ring, e.g. R₁ and R₂ may be joined to form a piperazine ring. This 5 to 7-membered heterocycloalkyl ring is preferably unsubstituted or substituted at one or two positions with a C₁₋₆ alkyl group, such as methyl or ethyl. The variable “Z” is preferably oxygen and the variable “A” is generally NH, CH═CH, or CH₂NH. Ar₁ and Ar₂ are preferably optionally substituted phenyl or optionally substituted pyridyl; optionally substituted 2-pyridyl is preferred for Ar₂. Substitutuents that may occur on Ar₁, and Ar₂ include, but are not limited to, butyl, isopropyl, trifluoromethyl, nitro, methyl, and halogen. Substitution at the 4 position of Ar₁ (when Ar₁ is phenyl or pyridyl) and substitution at the 3 position of Ar₂ (when Ar₂ is phenyl or pyridyl) are described in specific embodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention is particularly directed to compounds of Formula I, in which R₁ and R₂ independently represent hydrogen or lower alkyl, e.g., C₁₋₆ alkyl. Such compound will be referred to as compounds of Formula IA.

Preferred compounds and pharmaceutically acceptable salts of Formula IA are those wherein:

-   R₃ and R₄ are independently chosen at each occurrence from the group     consisting of hydrogen, halogen, cyano, nitro, haloalkyl,     haloalkoxy, hydroxy, amino, alkyl substituted with 0-2 R₆, alkenyl     substituted with 0-2 R₆; alkynyl substituted with 0-2 R₆; alkoxy     substituted with 0-2 R₆, —NH(alkyl) substituted with 0-2 R₆,     —N(alkyl)(alkyl) where each alkyl is independently substituted with     0-2 R₆, —XR₇, and Y;     or any two -   R₃ and R₄ not attached to the same carbon may be joined to form an     aryl ring substituted with 0-3 R₆, a saturated or partially     unsaturated carbocyclic ring of from 5 to 8 members, which     carbocyclic ring is substituted with 0-2 R₆, or a saturated,     partially unsaturated, or aromatic heterocyclic ring of from 5 to 8     members, which heterocyclic ring is substituted with 0-2 R₆ and     contains 1, 2, or 3 heteroatoms selected from N, O, and S; and -   Ar₁ and Ar₂ may be the same or different and are selected from the     group consisting of cyclohexyl, cyclopentyl, piperidinyl,     piperazinyl, phenyl, pyrrolyl, furanyl, thienyl, pyrazolyl,     imidazolyl, thiazolyl, isothiazolyl, oxazolyl, isoxazolyl,     oxadiazolyl, triazolyl, tetrazolyl, pyridyl, pyrimidyl, pyrazinyl,     benzimidazolyl, naphthyl, indolyl, isoindolyl, benzofuranyl,     isobenzofuranyl, benzo[b]thiophenyl, benz[d]isoxazolyl, quinolinyl,     isoquinolinyl, cinnolinyl, quinazolinyl, and quinoxalinyl, each of     which is optionally mono-, di-, or trisubstituted with R₅; or -   Ar₁ and Ar₂ may be the same or different and represent a bicyclic     oxygen-containing group of the formula:

-    optionally mono-, di-, or trisubstituted with R₅, where L     represents point of attachment and may be at any point on the     benzene ring, and the oxygen-containing ring of the bicyclic     oxygen-containing group consists of from 5 to 8 ring atoms, contains     1 or 2 oxygen atoms and remaining ring atoms are carbon; -   R₅ is independently selected at each occurrence from the group     consisting of halogen, cyano, nitro, haloalkyl, haloalkoxy, hydroxy,     amino, alkyl substituted with 0-2 R₆, alkenyl substituted with 0-2     R₆, alkynyl substituted with 0-2 R₆, alkoxy substituted with 0-2 R₆,     —NH(alkyl) substituted with 0-2 R₆, —N(alkyl)(alkyl) where each     alkyl is independently substituted with 0-2 R₆, —XR₇, and Y; -   R₆ is independently selected at each occurrence from the group     consisting of halogen, hydroxy, cyano, alkyl; alkoxy, —NH(alkyl),     —N(alkyl)(alkyl), —S(O)_(n)(alkyl), haloalkyl, haloalkoxy,     CO(alkyl), CONH(alkyl), CON(alkyl₁)(alkyl₂) where alkyl₁ and alkyl₂     may be joined to form a heterocycloalkyl ring of from 5 to 8 ring     atoms and containing 1, 2, or 3 heteroatoms selected from N, O, and     S, —XR₇, and Y; -   X is independently selected at each occurrence from the group     consisting of —CH₂—, —CHR₈—, —O—, —S(O)_(n)—, —NH—, —NR₈—, —C(═O)—,     —C(═O)O—, —C(═O)NH—, —C(═O)NR₈—, —S(O)_(n)NH—, —S(O)_(n)NR₈—,     NHC(═O)—, —NR₈C(═O)—, —NHS(O)_(n)—, and —NR₈S(O)_(n)—; -   R₇ and R₈ are independently selected at each occurrence from     hydrogen, and -    straight, branched, and cyclic alkyl groups, and (cycloalkyl)alkyl     groups, said straight, branched, and cyclic alkyl groups, and     (cycloalkyl)alkyl groups consisting of 1 to 8 carbon atoms, and     containing zero or one or more double or triple bonds, each of which     1 to 8 carbon atoms may be further substituted with one or more     substituent(s) independently selected from oxo, hydroxy, halogen,     amino, cyano, nitro, haloalkyl, haloalkoxy, —O(alkyl), —NH(alkyl),     —N(alkyl)(alkyl), —NHC(O)(alkyl), —N(alkyl)C(O)(alkyl),     —NHS(O)_(n)(alkyl), —S(O)_(n)(alkyl), —S(O)_(n)NH(alkyl),     —S(O)_(n)N(alkyl₃)(alkyl₄) where alkyl₃ and alkyl₄ may be joined to     form a heterocycloalkyl ring consisting of from 5 to 8 ring atoms     and containing 1, 2, or 3 heteroatoms selected from N, O, and S, and     Y′; -   Y and Y′ are independently selected at each occurrence from 3- to     8-membered carbocyclic or heterocyclic groups which are saturated,     unsaturated, or aromatic, which may be further substituted with one     or more substituents independently selected from halogen, oxo,     hydroxy, amino, nitro, cyano, alkyl, alkoxy, haloalkyl, haloalkoxy,     mono- or dialkylamino, and alkylthio; -    wherein said 3- to 8-membered heterocyclic groups contain one or     more heteroatom(s) independently selected from N, O, and S; and -   n is independently chosen at each occurrence from 0, 1, and 2. Such     compounds and pharmaceutically acceptable salts thereof, will be     referred to as compounds of Formula IB.

The invention is further directed to compounds of Formula II

and the pharmaceutically acceptable salts thereof, wherein:

-   A, Z, R₃, R₄ are as defined for Formula I or for Formula IB; Ar₁ and     Ar₂ are as defined for Formula I or for formula IB; and -    x is 1 or 3.

Preferred compounds and salts of Formula II are those in which

R_(A), R_(B), and R_(B)′ (which are contained in the definition of A) are independently selected at each occurrence from hydrogen or C₁₋₆alkyl.

Other preferred compounds salts of Formula II are those in which Z is oxygen, and those in which Z is oxygen and A is NH.

The invention is further directed to compounds of Formula III

and the pharmaceutically acceptable salts thereof, wherein:

-   G, Q, T, and W are the same or different and represent N, CH, or     CR₅, where R₅ is as defined for Formula IB; -   R_(A), R_(B), and R_(B)′ are independently selected at each     occurrence from hydrogen or C₁₋₆alkyl; -   Z is oxygen or sulfur; -   R₃ and R₄ are as defined for Formula I or for Formula IB; and -   x is 1 or 3.

The invention also included compounds of Formula IV

and the pharmaceutically acceptable salts thereof, wherein:

-   Z is S or O (preferably O); -   A, R₃ and R₄ is as defined for Formula I or Formula IB; -   Ar₁ and Ar₂ may be the same or different and are selected from the     group consisting of cyclohexyl, cyclopentyl, piperidinyl,     piperazinyl, pyrrolyl, furanyl, thienyl, pyrazolyl, imidazolyl,     thiazolyl, isothiazolyl, oxazolyl, isoxazolyl, oxadiazolyl,     triazolyl, tetrazolyl, pyridyl, pyrimidyl, pyrazinyl,     benzimidazolyl, naphthyl, indolyl, isoindolyl, benzofuranyl,     isobenzofuranyl, benzo[b]thiophenyl, benz[d]isoxazolyl, quinolinyl,     isoquinolinyl, cinnolinyl, quinazolinyl, and quinoxalinyl; wherein     Ar₁ is optionally mono-, di-, or trisubstituted with R₅, and Ar₂ is     optionally mono-, di-, or trisubstituted with R₉; or -    Ar₁ and Ar₂ may be the same or different and represent a bicyclic     oxygen-containing group as described for Formula IB, -   R₅ is independently selected at each occurrence from the group     consisting of cyano, nitro, haloalkyl, haloalkoxy, hydroxy, amino,     alkyl substituted with 0-2 R₆, alkenyl substituted with 0-2 R₆,     alkynyl substituted with 0-2 R₆, alkoxy substituted with 0-2 R₆,     —NH(alkyl) substituted with 0-2 R₆, —N(alkyl)(alkyl) where each     alkyl is independently substituted with 0-2 R₆, —XR₇, and Y; -   R₉ is independently selected at each occurrence from the group     consisting of cyano, nitro, haloalkoxy, hydroxy, amino, alkyl     substituted with 0-2 R₆, alkenyl substituted with 0-2 R₆, alkynyl     substituted with 0-2 R₆, alkoxy substituted with 0-2 R₆, —NH(alkyl)     substituted with 0-2 R₆, —N(alkyl)(alkyl) where each alkyl is     independently substituted with 0-2 R₆, —XR₇, and Y; and -   R₆, R₇, R₈, X Y and Y′ are as defined for Formula IB.

Another embodiment of the invention is directed to compounds of Formula V

and the pharmaceutically acceptable salt thereof, wherein:

-   G, Q, T, and W are the same or different and are selected from the     group consisting of N, CH, and CR₅, wherein T or W or both is N; -   A, R₃, and R₄ are as defined for Formula I or for Formula IB     (preferably A is —CH═CH—, —CH₂NH, NH, and R₃ and R₄ are hydrogen or     C₁₋₆ alkyl); -   Z is oxygen or sulfur (preferably oxygen); -   R₅ represents 1 to 3 substituents and is independently selected at     each occurrence from the group consisting of cyano, hydroxy, amino,     C₃₋₆ alkyl substituted with 0-2 R₆, C₂₋₆ alkenyl substituted with     0-2 R₆, C₂₋₆ alkynyl substituted with 0-2 R₆, C₃₋₆ alkoxy     substituted with 0-2 R₆, —NH(C₁₋₆alkyl) substituted with 0-2 R₆,     —N(C₁₋₆alkyl)(C₁₋₆alkyl) where each alkyl is independently     substituted with 0-2 R₆, —XR₇, and Y; -   R₉ represents 0 to 3 substituents and is independently selected at     each occurrence from the group consisting of halogen, cyano, nitro,     halo(C₁₋₆)alkyl, halo(C₁₋₆)alkoxy, hydroxy, amino, C₁₋₆alkyl     substituted with 0-2 R₆, C₂₋₆alkenyl substituted with 0-2 R₆,     C₂₋₆alkynyl substituted with 0-2 R₆, C₁₋₆alkoxy substituted with 0-2     R₆, —NH(C₁₋₆alkyl) substituted with 0-2 R₆, —N(C₁₋₆alkyl)(C₁₋₆alkyl)     where each C₁₋₆alkyl is independently substituted with 0-2 R₆, —XR₇,     and Y; -   R₆, R₇, R₈, X, Y, and Y′ are as defined for Formula IB.

The invention is particularly directed to compounds and salts of Formula V wherein G and Q are selected from the group consisting of CH and CR₅.

The invention is also directed to compounds and salts of Formula V wherein G, Q, and W are independently selected at each occurrence from the group consisting of CH and CR₅; and T is N.

For compounds of Formula V, particularly preferred R₆ substituents are halogen, hydroxy, C₁₋₄ alkyl, C₁₋₄ alkoxy, —NH(C₁₋₄alkyl), and —N(C₁₋₄ alkyl)(C₁₋₄ alkyl).

Still another embodiment of the invention is directed of compounds of Formula VI

and the pharmaceutically acceptable salts thereof, wherein:

-   A is selected from the group consisting of NH, —CH═CH—, and CH₂NH; -   R₄ is independently chosen from hydrogen and C₁₋₄ alkyl; -   R₅ represents 0 to 2 substituents and is independently chosen at     each occurrence from the group consisting of halogen, cyano, nitro,     halo(C₁₋₆)alkyl, halo(C₁₋₆)alkoxy, hydroxy, amino, C₁₋₆alkyl     substituted with 0-2 R₆, C₂₋₆alkenyl substituted with 0-2 R₆,     C₂₋₆alkynyl substituted with 0-2 R₆, C₁₋₆alkoxy substituted with 0-2     R₆, —NH(C₁₋₆alkyl) substituted with 0-2 R₆, —N(C₁₋₆alkyl)(C₁₋₆alkyl)     where each C₁₋₆alkyl is independently substituted with 0-2 R₆; -   R₉ represents 0 to 2 substituents and is independently chosen at     each occurrence from the group consisting of halogen, cyano, nitro,     halo(C₁₋₆)alkyl, halo(C₁₋₆)alkoxy, hydroxy, amino, C₁₋₆alkyl     substituted with 0-2 R₆, C₂₋₆alkenyl substituted with 0-2 R₆,     C₂₋₆alkynyl substituted with 0-2 R₆, C₁₋₆alkoxy substituted with 0-2     R₆, —NH(C₁₋₆alkyl) substituted with 0-2 R₆, and     —N(C₁₋₆alkyl)(C₁₋₆alkyl) where each C₁₋₆alkyl is independently     substituted with 0-2 R₆; -   R_(5A) is independently selected from the group consisting of     halogen, cyano, nitro, halo(C₁₋₆)alkyl, halo(C₁₋₆)alkoxy, hydroxy,     amino, C₁₋₆ alkyl, C₁₋₆ alkoxy, —NH(C₁₋₆ alkyl), and —N(C₁₋₆     alkyl)(C₁₋₆ alkyl); -   R_(9B) is independently selected from the group consisting of     halogen, nitro, halo(C₁₋₆)alkoxy, hydroxy, amino, C₁₋₆ alkyl, C₁₋₆     alkoxy, —NH(C₁₋₆ alkyl), and —N(C₁₋₆ alkyl)(C₁₋₆ alkyl) and -   R₆ is independently selected at each occurrence the group consisting     of halogen, hydroxy, C₁₋₄alkyl, C₁₋₄alkoxy, —NH(C₁₋₄ alkyl), and     —N(C₁₋₄ alkyl)(C₁₋₄ alkyl).

The invention is also directed to compounds of Formula VII

and the pharmaceutically acceptable salts thereof, wherein:

-   A, R₃, and R₄ are as defined for Formula I or for Formula IB; -   R₅ is independently selected at each occurrence from the group     consisting of cyano, nitro, haloalkyl, haloalkoxy, C₁₋₆ alkyl     substituted with 0-2 R₆, C₂₋₆ alkenyl substituted with 0-2 R₆, C₂₋₆     alkynyl substituted with 0-2 R₆, C₁₋₆ alkoxy substituted with 0-2     R₆, —NH(C₀₋₆ alkyl) substituted with 0-2 R₆, —N(C₁₋₆ alkyl)(C₁₋₆     alkyl) where each alkyl is independently substituted with 0-2 R₆,     —XR₇, and Y; -   R₉ represents 0-3 substituents and is independently selected at each     occurrence from the group consisting of bromo, haloalkyl,     haloalkoxy, hydroxy, C₂₋₆ alkyl substituted with 0-2 R₆, C₂₋₆     alkenyl substituted with 0-2 R₆, C₂₋₆ alkynyl substituted with 0-2     R₆, C₂₋₆ alkoxy substituted with 0-2 R₆, —NH(C₂₋₆ alkyl) substituted     with 0-2 R₆, —N(C₂₋₆ alkyl)(C₂₋₆ alkyl) where each C₂₋₆ alkyl is     independently substituted with 0-2 R₆, —XR₇, and Y; -   R₆, R₇, R₈, X, Y, and Y′ are as defined for Formula IB.

Preferred compounds and salts of Formula VII include those wherein A is selected from NH, —CH═CH—, and CH₂NH; and R₆ is independently selected at each occurrence from the group consisting of halogen, hydroxy, C₁₋₄ alkyl, C₁₋₄ alkoxy, —NH(C₁₋₄ alkyl), and —N(C₁₋₄ alkyl)(C₁₋₄ alkyl).

The invention includes compounds of Formula VIII

and the pharmaceutically acceptable salts thereof, wherein:

-   A is selected from the group consisting of NH, —CH═CH—, and CH₂NH     (NH is preferred); -   R₄ is independently selected at each occurrence from hydrogen and     C₁₋₄alkyl; -   R₅ represents 0 to 2 substituents independently selected at each     occurrence from the group consisting of halogen, cyano, nitro,     halo(C₁₋₆)alkyl, halo(C₁₋₆)alkoxy, hydroxy, amino, C₁₋₆alkyl     substituted with 0-2 R₆, C₂₋₆alkenyl substituted with 0-2 R₆,     C₂₋₆alkynyl substituted with 0-2 R₆, C₁₋₆alkoxy substituted with 0-2     R₆, —NH(C₁₋₆alkyl) substituted with 0-2 R₆, and     —N(C₁₋₆alkyl)(C₁₋₆alkyl) where each C₁₋₆alkyl is independently     substituted with 0-2 R₆; -   R₉ represents 0 to 2 substituents and is independently selected at     each occurrence from the group consisting of halogen, cyano, nitro,     halo(C₁₋₆)alkyl, halo(C₁₋₆)alkoxy, hydroxy, amino, C₁₋₆alkyl     substituted with 0-2 R₆, C₂₋₆alkenyl substituted with 0-2 R₆,     C₂₋₆alkynyl substituted with 0-2 R₆, C₁₋₆alkoxy substituted with 0-2     R₆, —NH(C₁₋₆alkyl) substituted with 0-2 R₆, and     —N(C₁₋₆alkyl)(C₁₋₆alkyl) where each C₁₋₆alkyl is independently     substituted with 0-2 R₆; -   R_(5A) is independently selected from the group consisting of     halogen, cyano, nitro, trifluoromethyl, trifluoromethoxy, hydroxy,     amino, C₁₋₆ alkyl, C₁₋₆ alkoxy, —NH(C₁₋₆ alkyl), and —N(C₁₋₆     alkyl)(C₁-C₆ alkyl); -   R_(9B) is independently selected from the group consisting of     trifluoromethoxy, hydroxy, C₂₋₆ alkyl, C₂₋₆ alkoxy, —NH(C₂₋₆ alkyl),     and —N(C₂₋₆ alkyl)(C₂₋₆ alkyl); and -   R₆ is independently selected at each occurrence from the group     consisting of halogen, hydroxy, C₁₋₄ alkyl, C₁₋₄ alkoxy, —NH(C₁₋₄     alkyl), and —N(C₁₋₄ alkyl)(C₁₋₄ alkyl).

Preferred compound of Formula VIII are those wherein one of R₄ is hydrogen and the other is methyl.

A particularly preferred embodiment of the invention includes compounds of Formula IX

and the pharmaceutically acceptable salts thereof, wherein:

-   A, R₃, and R₄ are as defined for Formula I or for Formula IB; -   R₅ is selected from the group consisting of bromo, fluoro, iodo,     halo(C₁₋₆)alkyl, halo(C₃₋₆)alkoxy, C₃₋₆alkyl substituted with 0-3     R₆, C₂₋₆alkenyl substituted with 0-3 R₆, C₂₋₆alkynyl substituted     with 0-3 R₆, C₃₋₆alkoxy substituted with 0-2 R₆,     (C₃₋₈cycloalkyl)C₁₋₄alkyl, —NH(C₁₋₆alkyl) substituted with 0-2 R₆,     —N(C₁₋₆alkyl)(C₁₋₆alkyl) where each C₁₋₆alkyl is substituted with     0-2 R₆, Y, —(C═O)Y, —(CH₂)Y, and —(CH(CN))Y; -   R₉ is selected from the group consisting of halogen, cyano,     —N(SO₂C₁₋₆alkyl)(SO₂C₁₋₆alkyl), —SO₂NH₂, halo(C₁₋₆)alkyl,     halo(C₁₋₆)alkoxy, C₁₋₆alkyl substituted with 0-2 R₆, C₂₋₆alkenyl     substituted with 0-2 R₆, C₂₋₆alkynyl substituted with 0-2 R₆,     C₁₋₆alkoxy substituted with 0-2 R₆, —NH(C₁₋₆alkyl) substituted with     0-2 R₆, —N(C₁₋₆alkyl)(C₁₋₆alkyl) where each C₁₋₆alkyl is substituted     with 0-2 R₆; -   R_(5B) and R_(9B) each represent from 0 to 2 substituents and are     independently selected at each occurrence from the group consisting     of halogen, cyano, nitro, halo(C₁₋₆)alkyl, halo(C₁₋₆)alkoxy,     hydroxy, amino, C₁₋₆alkyl substituted with 0-2 R₆,     (C₃₋₈cycloalkyl)C₁₋₄alkyl substituted with 0-2 R₆, C₂₋₆alkenyl     substituted with 0-2 R₆, C₂₋₆alkynyl substituted with 0-2 R₆,     C₁₋₆alkoxy substituted with 0-2 R₆, —NH(C₁₋₆alkyl) substituted with     0-2 R₆, and —N(C₁₋₆alkyl)(C₁₋₆alkyl) where each C₁₋₆alkyl is     independently substituted with 0-2 R₆, and Y; and any two -   R₅ and R_(5B) bound to adjacent atoms may be joined to form a     C₃₋₈cycloalkyl group or a heterocycloalkyl group, each of which is     optionally substituted by from 1 to 5 substituents independently     chosen from cyano, halogen, hydroxy, C₁₋₄alkyl, C₁₋₄alkoxy,     —NH(C₁₋₄alkyl), —N(C₁₋₄alkyl)(C₁₋₄alkyl), halo(C₁₋₄)alkyl, and     halo(C₁₋₄)alkoxy, wherein the heterocycloalkyl group consists of     from 4 to 8 atoms and contains 1, 2, or 3 heteroatoms selected from     N, Or and S; and -   R₆, R₇, R₈, X, Y, and Y′ are as defined for Formula IB.

Preferred compounds and salts of Formula IX are those wherein A is O or NR_(A), wherein R_(A) is hydrogen or methyl.

More preferred compounds and salts of Formula IX are those wherein

-   A is O or NR_(A), wherein R_(A) is hydrogen or methyl; and -   R₃ and R₄ are independently chosen at each occurrence from the group     consisting of hydrogen, halogen, cyano, nitro, halo(C₁₋₆)alkyl,     halo(C₁₋₆)alkoxy, hydroxy, amino, C₁₋₆alkyl, C₂₋₆alkenyl,     C₂₋₆alkynyl, C₁₋₆alkoxy, —NH(C₁₋₆alkyl), and     —N(C₁₋₆alkyl)(C₁₋₆alkyl).

Other preferred compounds and salts of Formula IX are those wherein:

-   A is O or NR_(A), wherein R_(A) is hydrogen or methyl; -   R₃ is hydrogen; and -   R₄ is independently chosen at each occurrence from the group     consisting of hydrogen, halogen, cyano, nitro, halo(C₁₋₆)alkyl,     halo(C₁₋₆)alkoxy, hydroxy, amino, C₁₋₆alkyl, C₂₋₆alkenyl,     C₂₋₆alkynyl, C₁₋₆alkoxy, —NH(C₁₋₆alkyl), and     —N(C₁₋₆alkyl)(C₁₋₆alkyl).

Still more preferred compounds and salts of Formula IX are those wherein

-   A is O, NR_(A), wherein R_(A) is hydrogen or methyl; -   R₃ is hydrogen; and -   R₄ is independently chosen at each occurrence from hydrogen and     C₁₋₆alkyl.

Another group of preferred compounds and salts of Formula IX is the group wherein

-   A is NR_(A), wherein R_(A) is hydrogen or methyl; -   R₃ is hydrogen; and -   R₄ is independently chosen at each occurrence from hydrogen,     halo(C₁₋₃)alkyl, and C₁₋₆alkyl, but more preferably R₄ is chosen     from hydrogen and C₁₋₄ alkyl.

A particular class of compounds of Formula IX is represented by Formula IX-A

and the pharmaceutically acceptable salts thereof, wherein:

-   R₅, R_(5B), R₉, and R_(9B) are as defined for Formula IX; and -   R₄ is independently chosen at each occurrence from hydrogen and     C₁₋₄alkyl.

Another class of compounds of Formula IX is represented by Formula IX-B:

and the pharmaceutically acceptably salts thereof, wherein:

-   R_(5B) and R_(9B) are independently chosen from hydrogen, halogen,     cyano, nitro, halo(C₁₋₂)alkyl, halo(C₁₋₂)alkoxy, amino, C₁₋₄alkyl,     and C₁₋₂alkoxy; and -   R₁₀ is independently chosen at each occurrence from hydrogen,     halogen, and C₁₋₄ alkyl.

Preferred compounds and salts of Formula IX-B are those wherein R₉ is selected from the group consisting of halogen, cyano, —N(SO₂CH₃)₂, —SO₂NH₂, halo(C₁₋₃)alkyl, C₁₋₃alkoxy, —NH(C₁₋₃alkyl), and —N(C₁₋₃alkyl)(C₁₋₃alkyl).

Other preferred compounds and salts of Formula IX-A and Formula IX-B are those wherein R_(5B) and R_(9B) are independently chosen from hydrogen, halogen, cyano, nitro, halo(C₁₋₂)alkyl, halo(C₁₋₂)alkoxy, amino,

-   C₁₋₄alkyl, and C₁₋₂alkoxy.

Still other preferred compounds and salts of Formula IX-A and Formula IX-B are those wherein:

-   R_(5B) represents 0 or 1 substituents chosen from halogen, cyano,     nitro, halo(C₁₋₂)alkyl, halo(C₁₋₂)alkoxy, amino, C₁₋₄alkyl, and     C₁₋₂alkoxy; and -   R_(9B), represents 0 or 1 substituents chosen from halogen, cyano,     nitro, halo(C₁₋₂)alkyl, and C₁₋₂alkyl, and C₁₋₂alkoxy.

The invention is further directed to compounds and salts of Formula IX-A and IX-E, wherein:

-   R₉ is selected from the group consisting of halogen, cyano,     —N(SO₂CH₃)₂, —SO₂NH₂, halo(C₁₋₃)alkyl, C₁₋₃alkoxy, —NH(C₁₋₃alkyl),     and —N(C₁₋₃alkyl)(C₁₋₃alkyl); -   R_(5B) represents 0 or 1 substituents chosen from halogen, cyano,     nitro, halo(C₁₋₂)alkyl, halo(C₁₋₂)alkoxy, amino, C₁₋₄alkyl, and     C₁₋₂alkoxy; and -   R_(9B) represents 0 or 1 substituents chosen from halogen, cyano,     nitro, halo(C₁₋₂)alkyl, and C₁₋₂alkyl, and C₁₋₂alkoxy.

For Formula IX-A, preferred substituents are

-   R₅ is selected from the group consisting of bromo, fluoro, iodo,     halo(C₁₋₆)alkyl, halo(C₃₋₆)alkoxy, C₃₋₆alkyl substituted with 0-3     R₆, C₂₋₆alkenyl substituted with 0-3 R₆, Y, —(C═O)Y, —(CH₂)Y, and     —(CH(CN))Y; -   R₉ is selected from the group consisting of halogen, cyano,     —N(SO₂CH₃)₂, —SO₂NH₂, halo(C₁₋₂)alkyl, C₁₋₃alkoxy, —NH(C₁₋₆alkyl),     and —N(C₁₋₆alkyl)(C₁₋₆alkyl); -   R_(5B) represents 0 or 1 substituents chosen from halogen, cyano,     nitro, halo(C₁₋₂)alkyl, halo(C₁₋₂)alkoxy, amino, C₁₋₄alkyl, and     C₁₋₂alkoxy; and -   R_(9B) represents 0 or 1 substituents chosen from halogen, cyano,     nitro, halo(C₁₋₂)alkyl, and C₁₋₂alkyl, and C₁₋₂alkoxy.

Particularly preferred definitions of R₆ for compounds and salts of this class are cyano, halogen, hydroxy, C₁₋₄alkyl, C₁₋₄alkoxy, —NH(C₁₋₄alkyl), and —N(C₁₋₄alkyl)(C₁₋₄alkyl) and Y; where

-   Y is independently selected at each occurrence from C₃₋₈ cycloalkyl,     piperidinyl, piperazinyl, tetrahydropyranyl, dihydropyranyl,     morpholinyl, thiomorpholinyl, phenyl, pyridyl, pyrazinyl,     pyrimidinyl, thiazolyl, thienyl, and imidazolyl, each of which may     be further substituted with one or more substituents independently     selected from halogen, oxo, hydroxy, amino, nitro, cyano, C₁₋₄alkyl,     C₁₋₄alkoxy, halo(C₁₋₄)alkyl, halo(C₁₋₄)alkoxy, mono- or     di(C₁₋₄)alkylamino, and C₁₋₄alkylthio.

Particularly preferred definitions of R₉ and R_(9B) for compounds of Formula IX-A are:

-   R₉ is cyano, trifluoromethyl, chloro, or iodo; and -   R_(9B) is hydrogen. -   Particularly preferred definitions of R₅ for compounds of Formula     IX-A are isopropyl, t-butyl, 2-butyl, trifluoromethyl, cyclopentyl,     cyclohexyl, and heptafluoropropyl.

The invention is particularly directed to compounds and pharmaceutically acceptable salts of Formula IB, Formula II, Formula III, Formula IV, Formula V, Formula VII and Formula IX in which:

-   R_(A), R_(B), and R_(B)′ are independently selected at each     occurrence from hydrogen and C₁₋₆alkyl; for the variables R₃, R₄,     and R₅ haloalkyl is halo(C₁₋₆)alkyl, i.e. a haloalkyl group having     from 1 to 6 carbon atoms and from 1 to maximum allowable number of     halogen substituents on those carbon atoms, haloalkoxy is     halo(C₁₋₆)alkoxy; alkyl is C₁₋₆alkyl, alkenyl is C₂₋₆alkenyl;     alkynyl is C₂₋₆alkynyl; alkoxy is C₁₋₆alkoxy, —NH(alkyl) is     —NH(C₁₋₆alkyl), and N(alkyl)(alkyl) is —N(C₁₋₆alkyl)(C₁₋₆alkyl), -   for the variables R₆, R₇, R₈, Y and Y′ alkyl is C₁₋₄alkyl, alkoxy     (or —O(alkyl) is C₁₋₄alkoxy for —O(C₁₋₄alkyl)), —NHalkyl (or     monoalkylamino) is —NH(C₁₋₄alkyl)(or mono(C₁₋₄alkyl)amino),     —N(alkyl)(alkyl) (also dialkylamino) is —N(C₁₋₄alkyl)(C₁₋₄alkyl)     (also di(C₁₋₄alkyl)amino), —S(O)_(n)alkyl is —S(O)_(n)(C₁₋₄alkyl),     haloalkyl is halo(C₁₋₄)alkyl, haloalkoxy is halo(C₁₋₄)alkoxy,     —CO(alkyl) is —CO(C₁₋₄alkyl), —CONH(alkyl) is —CONH(C₁₋₄alkyl), and     —CON(alkyl)(alkyl) is —CON(C₁₋₄alkyl₁)(C₁₋₄alkyl₂); —NHC(O)(alkyl)     is —NHC(O)(C₁₋₄alkyl), —N(alkyl)C(O)(alkyl) is —N(C₁₋₄alkyl)     C(O)(alkyl), —NHS(O)_(n)(alkyl) is —NHS(O)_(n)(C₁₋₄alkyl),     —S(O)_(n)NH(C₁₋₄alkyl), —S(O)_(n)N (alkyl)(alkyl) is     —S(O)_(n)N(C₁₋₄alkyl)(C₁₋₄alkyl); -   and alkylthio is C₁₋₄alkylthio.

Preferred compounds and salts of Formula V, Formula VI, Formula VII and Formula IX are those wherein R₃ and R₄ are independently selected at each occurrence from the group consisting of hydrogen and C₁₋₆ alkyl. More preferred compounds and salts of Formula V are those wherein R₃ is hydrogen and the R₄ substituents present on the 3 and 5 positions of the piperazine ring are hydrogen and the R₄ substituents on the 2 and 6 position of the piperazine ring are independently hydrogen or C₁₋₄ alkyl. For this discussion the piperazine ring is numbered as follows:

Even more preferred compounds and salts of Formula V are those wherein R₄ is methyl at the 2 position of the piperazine ring and R₃ and R₄ are hydrogen at all other positions.

The invention particularly includes compounds Formula A-1, Formula B-1, Formula C-1, Formula D-1, Formula E-1, and Formula F-1

-   and the pharmaceutically acceptable salts of Formula A-1, Formula     B-1, Formula C-1, Formula D-1, Formula E-1, and Formula F-1 wherein: -   R₅ and R₉ are independently selected from the group consisting of     halogen, cyano, nitro, halo(C₁₋₆)alkyl, halo(C₁₋₆)alkoxy, hydroxy,     amino, C₁₋₆alkyl, C₂₋₆alkenyl, C₂₋₆alkynyl, C₁₋₆alkoxy,     —NH(C₁₋₆alkyl, —N(C₁₋₆alkyl)(C₁₋₆alkyl), and C₃₋₈ cycloalkyl; and -   R_(5B) and R_(9B) each represent up to 2 substituents independently     selected at each occurrence from hydrogen, halogen, cyano, nitro,     halo(C₁₋₂)alkyl, halo(C₁₋₂)alkoxy, hydroxy, amino, C₁₋₃alkyl,     C₁₋₃alkoxy, —NH(C₁₋₃alkyl), and —N(C₁₋₆alkyl)(C₁₋₆alkyl).

Especially preferred compounds and salts of Formula A-1, Formula B-1, Formula C-1, Formula D-1, Formula E-1, and Formula F-1 are those wherein:

-   R₅ is C₃₋₆ alkyl; C₃₋₆ alkoxy; halo(C₁₋₃)alkyl, halo(C₁₋₃)alkoxy, or     C₃₋₈ cycloalkyl; -   R₉ is chloro or trifluomethyl; and -   R_(5B) and R_(9B) are hydrogen.

Representative compounds of the invention are shown in Table I below:

TABLE I Compound 1

Compound 2

Compound 3

Compound 4

Compound 5

Compound 6

In one aspect invention relates to diaryl piperazines and related compounds that bind with high affinity to capsaicin receptors, including human capsaicin receptors. Compounds that bind with high affinity for the capsaicin receptor include compounds exhibit K_(i) values of less than 10 uM, and preferably exhibit K_(i) values of less than 1 uM, more preferably exhibit K_(i) values of less than 100 nM, and most preferably exhibit K_(i) values of less than 10 nM at the capsaicin receptors. This invention also includes diaryl piperazines that bind with high selectivity to capsaicin receptor. Compounds that exhibit high selectivity for the capsaicin receptor exhibit at least 20-fold, and preferably at least 100-fold greater affinity for the capsaicin receptor than for other cell surface receptors (e.g., NPY Y5 receptors, NPY Y1 receptors, GABA_(A) receptors, MCH receptors, Bradykinin receptors, C5a receptors, androgen receptors, and the like).

Without wishing to be bound to any particular theory of operation, it is believed that the interaction of the compounds of Formulae I-IX and Formulae A-F with the capsaicin receptor results in the pharmaceutical utility of these compounds.

The invention further comprises methods of treating patients in need of such treatment with an amount of a compound of the invention sufficient to alter the symptoms of a disorder responsive to capsaicin receptor modulation. Thus, as used herein, the term treatment encompasses both disease modifying treatment and symptomatic treatment.

The diseases and/or disorders that can also be treated using compounds and compositions according to the invention (which are examples of disorders responsive to capsaicin receptor modulation) include:

Chronic and acute pain conditions, including toothache, postherpetic neuralgia, diabetic neuropathy, postmastectomy pain syndrome, stump pain (and phantom limb pain), reflex sympathetic dystrophy, trigeminal neuralgia, oral neuropathic pain, osteoarthritis, rheumatoid arthritis, fibromyalgia, Guillain-Barre syndrome, meralgia paresthetica, “burning-mouth” syndrome, and pain due to bilateral peripheral neuropathy. Preferred pain conditions for treatment in accordance with the invention are neuropathic pain conditions, including causalgia (reflex sympathetic dystrophy—RSD, secondary to injury of a peripheral nerve; this type of pain is generally considered to be non-responsive or only partially responsive to conventional opioid analgesic regimens), neuritis—including, e.g., sciatic neuritis, peripheral neuritis, polyneuritis, optic neuritis, postfebrile neuritis, migrating neuritis, segmental neuritis, Gombault's neuritis, and neuronitis, and neuralgias—including those mentioned above and, e.g., cervicobrachial neuralgia, cranial neuralgia, geniculate neuralgia, glossopharyngial neuralgia, migranous neuralgia, idiopathic neuralgia, intercostals neuralgia, mammary neuralgia, mandibular joint neuralgia, Morton's neuralgia, nasociliary neuralgia, occipital neuralgia, red neuralgia, Sluder's neuralgia, splenopalatine neuralgia, supraorbital neuralgia and vidian neuralgia. Additional pain conditions that can be treated in accordance with the invention include headache—particularly those involving peripheral nerve activity including, e.g., sinus, cluster (i.e., migranous neuralgia, supra) and some tension and migraine headache conditions—, labor pains, Charcot's pains, gas pains, menstrual pain, root pain, homotopic pain and heterotopic pain—including cancer associated pain, pain (and inflammation) associated with venom exposure, e.g., due to snake bite, spider bite, or insect sting, and traumatic, e.g., post-surgical pain and burn pain. A preferred condition that can be treated in accordance with the invention is pain (as well as broncho-constriction and inflammation) due to exposure (e.g., via ingestion, inhalation, or eye contact) of mucous membranes to capsaicin and related irritants such as tear gas, hot peppers, or pepper spray. Itching conditions, including psoriatic pruritis, itch due to hemodyalisis, aguagenic pruritus, and itching associated with vulvar vestibulitis, contact dermatitis, insect bites and skin allergies. Urinary incontenience, including detrusor hyperflexia of spinal origin and bladder hypersensitivity.

The invention also provides pharmaceutical compositions comprising compounds of the invention, including packaged pharmaceutical compositions for treating disorders responsive to capsaicin receptor modulation. The packaged pharmaceutical compositions include a container holding a therapeutically effective amount of at least one capsaicin receptor modulator as described supra and instructions (e.g., labeling) indicating the contained capsaicin receptor ligand is to be used for treating a disorder responsive to capsaicin receptor modulation in the patient.

The present invention also pertains to methods of inhibiting the binding of vanilloid (capsaicin analog) compounds, such as capsaicin, olvanil and RTX, to capsaicin receptors, which methods involve contacting a compound of the invention with cells expressing capsaicin receptors, wherein the compound is present at a concentration sufficient to inhibit vanilloid binding to capsaicin receptors in vitro. The methods of the invention include inhibiting the binding of vanilloid compounds to capsaicin receptors in vivo, e.g., in a patient given an amount of a compound of Formulae I-IX and Formulae A-F that results in and in vivo concentration in a body fluid sufficient to inhibit the binding of capsaicin compounds to capsaicin receptors in vitro. In one embodiment, such methods are useful in treating the effects of tear gas, hot pepper or pepper spray exposure. The amount of a compound that would be sufficient to inhibit the binding of a vanilloid compound to the capsaicin receptor may be readily determined via a capsaicin receptor binding assay, such as the assay described in Example 10 or by an assay of capsaicin receptor antagonism e.g., as in Example 11. The capsaicin receptors used to determine in vitro binding may be obtained from a variety of sources, for example from preparations of mammalian dorsal root ganglion (DRG) or from cells expressing cloned rat or human capsaicin receptors.

The present invention also pertains to methods for altering the signal-transducing activity, particularly the calcium ion conductance, mediated by capsaicin receptors, said method comprising exposing cells expressing such receptors to a solution comprising a compound of the, wherein the compound is present in the solution at a concentration sufficient to specifically alter the calcium conductance activity in response to capsaicin or RTX in vitro in cells expressing capsaicin receptors, preferred cells for this purpose are those that express high levels of capsaicin receptors (i.e., equal to or greater than the number of capsaicin receptors per cell found in rat DRG cells). This method includes altering the signal-transducing activity of capsaicin receptors in vivo. Preferably such alterations are reductions of calcium flux. The amount of a compound that would be sufficient to alter the signal-transducing activity of capsaicin receptors may be determined in vitro via a capsaicin receptor signal transduction assay, such as the calcium mobilization (conductance, flux) assay described in Example 11. The amount of a compound that would be sufficient to alter the calcium conductance activity in response to capsaicin or RTX of capsaicin receptors may also be determined via an assay of capsaicin receptor mediated calcium conductance, such as an assay wherein the binding of capsaicin to a cell surface capsaicin receptor effects changes in the fluorescence of a calcium sensitive dye or in the expression of a calcium sensitive reporter gene.

The invention further provides:

A method of reducing the calcium conductance of a capsaicin receptor, which method comprises:

contacting a first solution comprising a fixed concentration of a capsaicin receptor agonist and a compound or salt of the invention with a cell expressing the capsaicin receptor, wherein the compound or salt is present in the solution at a concentration sufficient to produce a detectable reduction of the calcium mobilization effects of the capsaicin receptor agonist when tested in an in vitro assay in which cells expressing a capsaicin receptor are contacted with a second solution comprising the fixed concentration of capsaicin receptor agonist and the compound or salt and the same method wherein: the cell expressing the capsaicin receptor is a neuronal cell that is contacted in vivo in an animal, and wherein the first solution is a body fluid of said animal; or the animal is a human patient.

A pharmaceutical composition comprising a pharmaceutically acceptable carrier and a compound or salt of the invention; and a package comprising the pharmaceutical composition in a container and further comprising indicia comprising instructions for using the composition to either alleviate pain; or to treat a patient suffering from urinary incontinence or to alleviate symptoms of exposure to capsaicin or tear gas.

A compound or salt of the invention wherein, in an in vitro assay of capsaicin receptor antagonism, the compound or salt exhibits capsaicin receptor antagonist activity, but in an in vitro assay of capsaicin receptor agonism the compound does not exhibit detectable agonist activity.

A compound or salt of the invention wherein a dose of the compound or salt sufficient to provide analgesia in an animal model for determining pain relief does not produce sedation in an animal model assay of sedation.

A method of treating a mammal suffering from at least one symptom selected from the group consisting of symptoms of exposure to capsaicin, symptoms of burns or irritation due to exposure to heat, symptoms of burns or irritation due to exposure to light, symptoms of burns or irritation due to exposure to tear gas, and symptoms of burns or irritation due to exposure to acid, the method comprising administering to the mammal a therapeutic dose of a compound that:

-   a) is a high potency capsaicin receptor antagonist in an in vitro     assay of capsaicin receptor antagonism, -   b) exhibits no detectable agonist activity in an in vitro assay of     capsaicin receptor agonism, -   c) is not a capsaicin analog, and -   d) when administered to an animal in an animal model assay of     sedation, at five times the minimum dosage needed to provide     analgesia in an animal model for determining pain relief, does not     cause sedation,     wherein the therapeutic dose contains an amount of the compound that     is effective to reduce severity of at least one of the at least one     symptom and preferably wherein the compound is a compound of the     invention.

A method of treating a mammal suffering from neuropathic pain, the method comprising administering to the mammal a therapeutic dose of a compound that is a capsaicin receptor antagonist, and in certain embodiments, wherein the compound is a compound of the invention.

A method of treating a mammal suffering from peripheral-nerve-mediated pain, e.g., neuropathic pain, the method comprising administering to the mammal a therapeutic dose of a compound that is a capsaicin receptor antagonist, wherein the compound:

-   a) is a high potency capsaicin receptor antagonist in an in vitro     assay of capsaicin receptor antagonism, -   b) exhibits no detectable agonist activity in an in vitro assay of     capsaicin receptor agonism, -   c) is not a capsaicin analog, and -   d) when administered to an animal in an animal model assay of     sedation, at five times the minimum dosage needed to provide     analgesia in an animal model for determining pain relief, does not     cause sedation,

wherein the therapeutic dose contains an amount of the compound that is effective to reduce the peripheral-nerve-mediated pain, and preferably wherein the pain is neuropathic pain and the compound is a compound of the invention, and preferably wherein the pain is associated with a condition selected from the group consisting of postmastectomy pain syndrome, stump pain, phantom limb pain, oral neuropathic pain, Charcot's pain, toothache, postherpetic neuralgia, diabetic neuropathy, reflex sympathetic dystrophy, trigeminal neuralgia, osteoarthritis, rheumatoid arthritis, fibromyalgia, Guillain-Barre syndrome, meralgia paresthetica, burning-mouth syndrome, bilateral peripheral neuropathy, causalgia, sciatic neuritis, peripheral neuritis, polyneuritis, optic neuritis, postfebrile neuritis, migrating neuritis, segmental neuritis, Gombault's neuritis, neuronitis, cervicobrachial neuralgia, cranial neuralgia, geniculate neuralgia, glossopharyngial neuralgia, migranous neuralgia, idiopathic neuralgia, intercostals neuralgia, mammary neuralgia, mandibular joint neuralgia, Morton's neuralgia, nasociliary neuralgia, occipital neuralgia, red neuralgia, Sluder's neuralgia, splenopalatine neuralgia, supraorbital neuralgia, vidian neuralgia, sinus headache, tension headache, labor, childbirth, intestinal gas, menstruation, cancer, and trauma.

A compound of the invention, wherein the compound is not addictive.

The capsaicin receptor ligands provided by this invention and labeled derivatives thereof are also useful as standards and reagents for determining the ability of a compound to bind to the capsaicin receptor and to act as an agonist, antagonist, inverse agonist, mixed agonist/antagonist or the like.

More particularly compounds of the invention may be used for demonstrating the presence of VR1 receptors or other capsaicin receptors in cell or tissue samples. This may be done by preparing a plurality of matched cell or tissue samples, at least one of which is prepared as an experimental sample and at least one of which is prepared as a control sample. The experimental sample is prepared by contacting (under conditions that permit binding of capsaicin or RTX to capsaicin receptors within cell and tissue samples) at least one of the matched cell or tissue samples that has not previously been contacted with any compound or salt of the invention with an experimental solution comprising the detectably-labeled preparation of the selected compound or salt at a first measured molar concentration. The control sample is prepared by in the same manner as the experimental sample and is incubated in a solution that contains the same ingredients as the experimental solution but that also contains an unlabelled preparation of the same compound or salt of the invention at a molar concentration that is greater than the first measured molar concentration.

The experimental and control samples are then washed (using the same wash conditions) to remove unbound detectably-labeled compound. The amount of detectably-labeled compound remaining bound to each sample is then measured and the amount of detectably-labeled compound in the experimental and control samples is compared. A comparison that indicates the detection of a greater amount of detectable label in the at least one washed experimental sample than is detected in any of the at least one washed control samples demonstrates the presence of capsaicin receptors in that experimental sample.

The detectably-labeled compound used in this procedure may be labeled with any detectable label, such as a radioactive label, a biological tag such as biotin (which can be detected by binding to detectably-labeled avidin), an enzyme (e.g., alkaline phosphatase, beta galactosidase, or a like enzyme that can be detected its activity in a calorimetric, luminescent, or like assay) or a directly or indirectly luminescent label. When tissue sections are used in this procedure and the detectably-labeled compound is radiolabeled, the bound, labeled compound may be detected autoradiographically to generate an autoradiogram. When autoradiography is used, the amount of detectable label in an experimental or control sample may be measured by viewing the autoradiograms and comparing the exposure density of matched regions of the autoradiograms.

Labeled derivatives the capsaicin receptor ligands provided by this invention are also useful as radiotracers for positron emission tomography (PET) imaging or for single photon emission computerized tomography (SPECT) to characterize and localize capsaicin receptors in vivo.

DEFINITIONS

The compounds herein described may have one or more asymmetric centers or planes. Compounds of the present invention containing an asymmetrically substituted atom may be isolated in optically active or racemic forms. It is well known in the art how to prepare optically active forms, such as by resolution of racemic forms (racemates), by asymmetric synthesis, or by synthesis from optically active starting materials. Resolution of the racemates can be accomplished, for example, by conventional methods such as crystallization in the presence of a resolving agent, or chromatography, using, for example a chiral HPLC column. Many geometric isomers of olefins, C═N double bonds, and the like can also be present in the compounds described herein, and all such stable isomers are contemplated in the present invention. Cis and trans geometric isomers of the compounds of the present invention are described and may be isolated as a mixture of isomers or as separated isomeric forms. All chiral (enantiomeric and diastereomeric), and racemic forms, as well as all geometric isomeric forms of a structure are intended, unless the specific stereochemistry or isomeric form is specifically indicated.

The term “substituted,” as used herein, means that any one or more hydrogens on the designated atom is replaced with a selection from the indicated group, provided that the designated atom's normal valence is not exceeded, and that the substitution results in a stable compound. The present invention is intended to include all isotopes of atoms occurring in the present compounds. Isotopes include those atoms having the same atomic number but different mass numbers, By way of general example and without limitation, isotopes of hydrogen include tritium and deuterium. Isotopes of carbon include ¹¹C, ¹³C, and ¹⁴C.

When any variable occurs more than one time in any constituent or formula for a compound, its definition at each occurrence is independent of its definition at every other occurrence. Thus, for example, if a group is shown to be substituted with 0-2 R*, then said group may optionally be substituted with up to two R* groups and R* at each occurrence is selected independently from the definition of R*. Also, combinations of substituents and/or variables are permissible only if such combinations result in stable compounds.

As indicated above, various substituents of the various formulae are “optionally substituted”, including Ar₁, Ar₂, R₃ and R₄ of Formulae I-IX and Formulae A-F, and such substituents as recited in the sub-formulae such as Formula Ia and the like. When substituted, those substituents (e.g., C₁₋₆ alkyl, n, Ar₁, Ar₂, R₁, R₂, R₃, and R₄) may be substituted by other than hydrogen at one or more available positions, typically 1 to 3 or 4 positions, by one or more groups, such as, halogen such as fluoro, chloro, bromo and iodo; cyano; hydroxyl; nitro; azido; alkanoyl such as a C₁₋₆ alkanoyl group such as acyl and the like; carboxamido; alkyl groups including those groups having 1 to about 12 carbon atoms, or 1, 2, 3, 4, 5, or 6 carbon atoms; alkenyl and alkynyl groups including groups having one or more unsaturated linkages and from 2 to about 12 carbon, or 2, 3, 4, 5 or 6 carbon atoms; alkoxy groups having those having one or more oxygen linkages and from 1 to about 12 carbon atoms, or 1, 2, 3, 4, 5 or 6 carbon atoms; aryloxy such as phenoxy; alkylthio groups including those moieties having one or more thioether linkages and from 1 to about 12 carbon atoms, or 1, 2, 3, 4, 5 or 6 carbon atoms; alkylsulfinyl groups including those moieties having one or more sulfinyl linkages and from 1 to about 12 carbon atoms, or 1, 2, 3, 4, 5, or 6 carbon atoms; alkylsulfonyl groups including those moieties having one or more sulfonyl linkages and from 1 to about 12 carbon atoms, or 1, 2, 3, 4, 5, or 6 carbon atoms; aminoalkyl groups such as groups having one or more N atoms and from 1 to about 12 carbon atoms, or 1, 2, 3, 4, 5 or 6 carbon atoms; carbocyclic aryl having 6 or more carbons, particularly phenyl (e.g. an Ar group being a substituted or unsubstituted biphenyl moiety); arylalkyl having 1 to 3 separate or fused rings and from 6 to about 18 carbon ring atoms, with benzyl being a preferred group; arylalkoxy having 1 to 3 separate or fused rings and from 6 to about 18 carbon ring atoms, with O-benzyl being a preferred group; or a heteroaromatic or heteroalicyclic group having 1 to 3 separate or fused rings with 3 to about 8 members per ring and one or more N, O or S atoms, e.g. coumarinyl, quinolinyl, pyridyl, pyrazinyl, pyrimidyl, furyl, pyrrolyl, thienyl, thiazolyl, oxazolyl, imidazolyl, indolyl, benzofuranyl, benzothiazolyl, tetrahydrofuranyl, tetrahydropyranyl, piperidinyl, morpholino and pyrrolidinyl.

As used herein, “alkyl” is intended to include both branched, straight-chain, and cyclic alkyl groups, having the specified number of carbon atoms that may contain one or more double or triple bonds. “Lower alkyl” denotes an alkyl group having from 1 to about 6 carbon atoms. Examples of alkyl include, but are not limited to, methyl, ethyl, n-propyl, i-propyl, n-butyl, s-butyl, t-butyl, n-pentyl, and s-pentyl. Preferred alkyl groups are C₁-C₆ alkyl groups. Especially preferred alkyl groups are methyl, ethyl, propyl, butyl, 3-pentyl.

As used herein, “alkoxy”, “C₁-C₆ alkoxy”, or “lower alkoxy” in the present invention is meant an alkyl group attached through an oxygen bridge such as, for example, methoxy, ethoxy, propoxy, isopropoxy, n-butoxy, sec-butoxy, tert-butoxy, pentoxy, 2-pentyl, isopentoxy, neopentoxy, hexoxy, 2-hexoxy, 3-hexoxy, and 3-methylpentoxy. “Lower alkoxy” denotes an alkyl group having from 1 to about 6 carbon atoms.

“Haloalkyl” is intended to include both branched and straight-chain saturated aliphatic hydrocarbon groups having the specified number of carbon atoms, substituted with 1 or more halogen (for example —C_(v)F_(W) where v=1 to 3 and w=1 to (2v+1). Examples of haloalkyl include, but are not limited to, trifluoromethyl, trichloromethyl, pentafluoroethyl, heptafluoropropyl, and pentachloroethyl.

As used herein, “carbocycle” or “carbocyclic ring” is intended to mean any stable 3- to 7-membered monocyclic or bicyclic or 7- to 13-membered bicyclic or tricyclic moeity, any of which may be saturated, partially unsaturated, or aromatic. Examples of such carbocycles include, but are not limited to, cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, adamantyl, cyclooctyl, [3.3.0]bicyclooctane, [4.3.0]bicyclononane, [4.4.0]bicyclodecane, [2.2.2]bicyclooctane, fluorenyl, phenyl, naphthyl, indanyl, adamantyl, and tetrahydronaphthyl.

As used herein, the term “carbocyclic aryl” indicates aromatic groups containing only carbon. Such aromatic groups may be further substituted.

As used herein, the term “heterocyclic ring” is intended to mean a stable 5- to 7-membered monocyclic or bicyclic or 7- to 10-membered bicyclic heterocyclic ring which is saturated, partially unsaturated, or unsaturated (aromatic), and which consists of carbon atoms and from 1 to 4 heteroatoms independently selected from the group consisting of N, 0 and S and including any bicyclic group in which any of the above-defined heterocyclic rings is fused to a benzene ring. The nitrogen and sulfur heteroatoms may optionally be oxidized. The heterocyclic ring may be attached to its pendant group at any heteroatom or carbon atom that results in a stable structure. The heterocyclic rings described herein may be substituted on carbon or on a nitrogen atom if the resulting compound is stable. A nitrogen atom in the heterocycle may optionally be quaternized. It is preferred that when the total number of S and 0 atoms in the heterocycle exceeds 1, then these heteroatoms are not adjacent to one another. It is preferred that the total number of S and 0 atoms in the heterocycle is not more than 1. As used herein, the term “heteroaryl” is intended to mean a stable 5- to 7-membered monocyclic or bicyclic or 7- to 10-membered bicyclic heterocyclic aromatic ring which consists of carbon atoms and from 1 to 4 heteroatoms independently selected from the group consisting of N, O and S. It is preferred that the total number of S and O atoms in the aromatic heterocycle. is not more than 1. The term “heterocycloalkyl” is intended to mean a stable 5- to 7-membered monocyclic or bicyclic or 7- to 10-membered bicyclic heterocyclic saturated ring which consists of carbon atoms and from 1 to 4 heteroatoms independently selected from the group consisting of N, O and S. Examples of heterocycles include, but are not limited to, acridinyl, azocinyl, benzimidazolyl, benzofuranyl, benzothiofuranyl, benzothiophenyl, benzoxazolyl, benzthiazolyl, benztriazolyl, benztetrazolyl, benzisoxazolyl, benzisothiazolyl, benzimidazolinyl, carbazolyl, NH-carbazolyl, carbolinyl, chromanyl, chromenyl, cinnolinyl, decahydroquinolinyl, 2H,6H-1,5,2-dithiazinyl, dihydrofuro[2,3-b]tetrahydrofuran, furanyl, furazanyl, imidazolidinyl, imidazolinyl, imidazolyl, 1H-indazolyl, indolenyl, indolinyl, indolizinyl, indolyl, 3H-indolyl, isobenzofuranyl, isochromanyl, isoindazolyl, isoindolinyl, isoindolyl, isoquinolinyl, isothiazolyl, isoxazolyl, morpholinyl, naphthyridinyl, octahydroisoquinolinyl, oxadiazolyl, 1,2,3-oxadiazolyl, 1,2,4-oxadiazolyl; -1,2,5-oxadiazolyl, 1,3,4-oxadiazolyl, oxazolidinyl, oxazolyl, oxazolidinyl, pyrimidinyl, phenanthridinyl, phenanthrolinyl, phenazinyl, phenothiazinyl, phenoxathiinyl, phenoxazinyl, phthalazinyl, piperazinyl, piperidinyl, pteridinyl, purinyl, pyranyl, pyrazinyl, pyrazolidinyl, pyrazolinyl, pyrazolyl, pyridazinyl, pyridooxazole, pyridoimidazole, pyridothiazole, pyridinyl, pyridyl, pyrimidinyl, pyrrolidinyl, pyrrolinyl, 2H-pyrrolyl, pyrrolyl, quinazolinyl, quinolinyl, 4H-quinolizinyl, quinoxalinyl, quinuclidinyl, tetrahydrofuranyl, tetrahydroisoquinolinyl, tetrahydroquinolinyl, 6H-1,2,5-thiadiazinyl, 1,2,3-thiadiazolyl, 1,2,4-thiadiazolyl, 1,2,5-thiadiazolyl, 1,3,4thiadiazolyl, thianthrenyl, thiazolyl, thienyl, thienothiazolyl, thienooxazolyl, thienoimidazolyl, thiophenyl, triazinyl, 1,2,3-triazolyl, 1,2,4-triazolyl, 1,2,5-triazolyl, 1,3,4-triazolyl, and xanthenyl.

Preferred heterocycles include, but are not limited to, pyrrolyl, furanyl, thienyl, pyrazolyl, imidazolyl, thiazolyl, isothiazolyl, oxazolyl, isoxazolyl, oxadiazolyl, triazolyl, tetrazolyl, pyridyl, pyrimidyl, pyrazinyl, benzimidazolyl, indolyl, isoindolyl, benzofuranyl, isobenzofuranyl, benzo[b]thiophenyl, benz[d]isoxazolyl, quinolinyl, isoquinolinyl, cinnolinyl, quinazolinyl, or quinoxalinyl. Also included are fused ring and spiro compounds containing, for example, the above heterocycles.

The term “bicyclic oxygen-containing group” is meant to encompass a particular type of heteroaryl group of the formula:

where L indicates the point of attachment of the group to the structure of Formulae I-IX and Formulae A-F. The heterocyclic oxygen-containing ring has a total of from 5 to 7 members, and is saturated or unsaturated. Either ring of the bicyclic oxygen-containing group may be further substituted.

Examples of bicyclic oxygen-containing groups include any or all of the following structures:

Pharmaceutical Preparations

Those skilled in the art will recognize various synthetic methodologies that may be employed to prepare non-toxic pharmaceutically acceptable prodrugs of the compounds encompassed by Formulae I-IX and Formulae A-F, which prodrugs are encompassed by the present invention. “Prodrugs” are intended to include any compounds that become compounds of Formulae I-IX and Formulae A-F when administered to a mammalian subject, e.g., upon metabolic processing of the prodrug. Examples of prodrugs include, but are not limited to, acetate, formate and benzoate and like derivatives of functional groups (such as alcohol or amine groups) in the compounds of Formulae I-IX and Formulae A-F. Those skilled in the art will recognize a wide variety of nontoxic pharmaceutically acceptable solvents that may be used to prepare solvates of the compounds of the invention, such as water, ethanol, mineral oil, vegetable oil, and dimethylsulfoxide.

The compounds of general Formulae I-IX and general Formulae A-F may be administered orally, topically, parenterally, e.g., by inhalation or spray or rectally in dosage unit formulations containing conventional non-toxic pharmaceutically acceptable carriers, adjuvants and vehicles. Oral administration in the form of a pill, capsule, elixir, syrup, lozenge, troche, or the like is particularly preferred. The term parenteral as used herein includes subcutaneous injections, intradermal, intravascular (e.g., intravenous), intramuscular, spinal, intrathecal injection or like injection or infusion techniques. In addition, there is provided a pharmaceutical formulation comprising a compound of general Formulae I-IX and general Formulae A-F and a pharmaceutically acceptable carrier. One or more compounds of general Formulae I-IX and general Formulae A-F may be present in association with one or more non-toxic pharmaceutically acceptable carriers and/or diluents and/or adjuvants and if desired other active ingredients. The pharmaceutical compositions containing compounds of general Formulae I-IX and general Formulae A-F may be in a form suitable for oral use, for example, as tablets, troches, lozenges, aqueous or oily suspensions, dispersible powders or granules, emulsion, hard or soft capsules, or syrups or elixirs.

Compositions intended for oral use may be prepared according to any method known to the art for the manufacture of pharmaceutical compositions and such compositions may contain one or more agents selected from the group consisting of sweetening agents, flavoring agents, coloring agents and preserving agents in order to provide pharmaceutically elegant and palatable preparations. Tablets contain the active ingredient in admixture with non-toxic pharmaceutically acceptable excipients that are suitable for the manufacture of tablets. These excipients may be for example, inert diluents, such as calcium carbonate, sodium carbonate, lactose, calcium phosphate or sodium phosphate; granulating and disintegrating agents, for example, corn starch, or alginic acid; binding agents, for example starch, gelatin or acacia, and lubricating agents, for example magnesium stearate, stearic acid or talc. The tablets may be uncoated or they may be coated by known techniques to delay disintegration and absorption in the gastrointestinal tract and thereby provide a sustained action over a longer period. For example, a time delay material such as glyceryl monosterate or glyceryl distearate may be employed.

Formulations for oral use may also be presented as hard gelatin capsules wherein the active ingredient is mixed with an inert solid diluent, for example, calcium carbonate, calcium phosphate or kaolin, or as soft gelatin capsules wherein the active ingredient is mixed with water or an oil medium, for example peanut oil, liquid paraffin or olive oil.

Aqueous suspensions contain the active materials in admixture with excipients suitable for the manufacture of aqueous suspensions. Such excipients are suspending agents, for example sodium carboxymethylcellulose, methylcellulose, hydropropylmethylcellulose, sodium alginate, polyvinylpyrrolidone, gum tragacanth and gum acacia; dispersing or wetting agents may be a naturally-occurring phosphatide, for example, lecithin, or condensation products of an alkylene oxide with fatty acids, for example polyoxyethylene stearate, or condensation products of ethylene oxide with long chain aliphatic alcohols, for example heptadecaethyleneoxycetanol, or condensation products of ethylene oxide with partial esters derived from fatty acids and a hexitol such as polyoxyethylene sorbitol monooleate, or condensation products of ethylene oxide with partial esters derived from fatty acids and hexitol anhydrides, for example polyethylene sorbitan monooleate. The aqueous suspensions may also contain one or more preservatives, for example ethyl, or n-propyl p-hydroxybenzoate, one or more coloring agents, one or more flavoring agents, and one or more sweetening agents, such as sucrose or saccharin.

Oily suspensions may be formulated by suspending the active ingredients in a vegetable oil, for example arachis oil, olive oil, sesame oil or coconut oil, or in a mineral oil such as liquid paraffin. The oily suspensions may contain a thickening agent, for example beeswax, hard paraffin or cetyl alcohol. Sweetening agents such as those set forth above, and flavoring agents may be added to provide palatable oral preparations. These compositions may be preserved by the addition of an anti-oxidant such as ascorbic acid.

Dispersible powders and granules suitable for preparation of an aqueous suspension by the addition of water provide the active ingredient in admixture with a dispersing or wetting agent, suspending agent and one or more preservatives. Suitable dispersing or wetting agents and suspending agents are exemplified by those already mentioned above. Additional excipients, for example sweetening, flavoring and coloring agents, may also be present.

Pharmaceutical compositions of the invention may also be in the form of oil-in-water emulsions. The oily phase may be a vegetable oil, for example olive oil or arachis oil, or a mineral oil, for example liquid paraffin or mixtures of these. Suitable emulsifying agents may be naturally-occurring gums, for example gum acacia or gum tragacanth, naturally-occurring phosphatides, for example soy bean, lecithin, and esters or partial esters derived from fatty acids and hexitol, anhydrides, for example sorbitan monoleate, and condensation products of the said partial esters with ethylene oxide, for example polyoxyethylene sorbitan monoleate. The emulsions may also contain sweetening and flavoring agents.

Syrups and elixirs may be formulated with sweetening agents, for example glycerol, propylene glycol, sorbitol or sucrose. Such formulations may also contain a demulcent, a preservative and flavoring and coloring agents. The pharmaceutical compositions may be in the form of a sterile injectable aqueous or oleaginous suspension. This suspension may be formulated according to the known art using those suitable dispersing or wetting agents and suspending agents which have been mentioned above. The sterile injectable preparation may also be sterile injectable solution or suspension in a non-toxic parentally acceptable diluent or solvent, for example as a solution in 1,3-butanediol. Among the acceptable vehicles and solvents that may be employed are water, Ringer's solution and isotonic sodium chloride solution. In addition, sterile, fixed oils are conventionally employed as a solvent or suspending medium. For this purpose any bland fixed oil may be employed including synthetic mono- or diglycerides. In addition, fatty acids such as oleic acid find use in the preparation of injectables.

The compounds of general Formulae I-IX and general Formulae A-F may also be administered in the form of suppositories, e.g., for rectal or vaginal administration of the drug. These compositions can be prepared by mixing the drug with a suitable non-irritating excipient that is solid at ordinary temperatures but liquid at the rectal temperature and will therefore melt in the rectum to release the drug. Such materials are cocoa butter and polyethylene glycols.

Compounds of general Formulae I-IX and general Formulae A-F may be administered parenterally in a sterile medium. The drug, depending on the vehicle and concentration used, can either be suspended or dissolved in the vehicle. Advantageously, adjuvants such as local anesthetics, preservatives and buffering agents can be dissolved in the vehicle where desirable.

Typical subjects to which compounds of the invention may be administered will be mammals, particularly primates, especially humans. For veterinary applications, a wide variety of subjects will be suitable, e.g. livestock such as cattle, sheep, goats, cows, swine and the like; poultry such as chickens, ducks, geese, turkeys, and the like; and other domesticated animals particularly pets (companion animals) such as dogs and cats. For diagnostic or research applications, a wide variety of mammals will be suitable subjects including rodents (e.g. mice, rats, hamsters), rabbits, primates, and swine such as inbred pigs and the like.

For administration to non-human animals, the composition may also be added to the animal feed or drinking water. It will be convenient to formulate these animal feed and drinking water compositions so that the animal takes in an appropriate quantity of the composition along with its diet. It will also be convenient to present the composition as a premix for addition to the feed or drinking water.

For systemic (as opposed to local or topical) administration, dosage levels of the order of from about 0.01 mg to about 140 mg per kilogram of body weight per day are useful in the treatment of pain, urinary incontinence, or other of the above-indicated conditions (about 0.05 mg to about 7 g per human patient per day). Preferred systemic doses for preferred high potency compounds of Formulae I-IX and Formulae A-F range from about 0.01 mg to about 50 mg per kilogram of body weight per subject per day, with oral doses generally being about 5-20 fold higher than intravenous doses. The most highly preferred compounds of the invention are orally active (e.g., provide a reduction of pain or a reduction of frequency of urinary incontinence) at doses ranging from 0.05 to 40 mg per kilogram of body weight per subject per day.

The amount of active ingredient that may be combined with the carrier materials to produce a single dosage form will vary depending upon the host treated and the particular mode of administration. Dosage unit forms will generally contain between from about 1 mg to about 500 mg of an active ingredient.

Frequency of dosage may also vary depending on the compound used and the particular disease treated. However, for treatment of most disorders, a dosage regimen (frequency of administration) of 4 times daily or less is preferred. For the treatment of chronic pain or urinary incontinence a dosage regimen of 2 times daily is more preferred and a frequency of administration of once a day is particularly preferred. For the treatment of acute pain a single dose that rapidly reaches effective concentrations is desirable.

It will be understood, however, that the specific dose level for any particular patient will depend upon a variety of factors including the activity of the specific compound employed, the age, body weight, general health, sex, diet, time of administration, route of administration, and rate of excretions drug combination and the nature and severity of the particular disease or condition undergoing treatment.

Preferred compounds of the invention will have certain desirable pharmacological properties. For systemic administration such properties include, but are not limited to high oral bioavailability, such that the preferred oral dosages and dosage forms discussed above can provide therapeutically effective levels of the compound in vivo, low serum protein binding and low first pass hepatic metabolism. For all types of administration low toxicity, and desirable in vitro and in vivo half-lives are desired. While penetration of the blood brain barrier for compounds used to treat CNS disorders is necessary low brain levels of compounds used to treat peripheral disorders (such as urinary incontinence, or chronic or acute pain that does not originate from the CNS) are often preferred.

Laboratory assays may be used to predict these desirable pharmacological properties. The discussion that follows is supplemented by the detailed protocols of Example 16, infra. Assays used to predict bioavailability include transport across human intestinal cell monolayers, including Caco-2 cell monolayers. Toxicity to cultured hepatocyctes may be used to predict compound toxicity, with non-toxic compounds being preferred. Penetration of the blood brain barrier of a compound in humans may be predicted from the brain levels of the compound in laboratory animals given the compound, e.g., intravenously.

Percentage of serum protein binding may be predicted from albumin binding assays. Examples of such assays are described in a review by Oravcová, et al. (Journal of Chromatography B (1996) volume 677, pages 1-27). Preferred compounds exhibit reversible serum protein binding. Preferably this binding is less than 99%, more preferably less than 95%, even more preferably less than 90%, and most preferably less than 80%.

Frequency of administration is generally inversely proportional to the in vivo half-life of a compound. In vivo half-lives of compounds may be predicted from the results of assays, e.g., in vitro assays of microsomal half-life as described by Kuhnz and Gieschen (Drug Metabolism and Disposition, 1998, volume 26, pages 1120-1127). Preferred half-lives are those allowing for a preferred frequency of administration.

Preparation of Compounds

The compounds of the present invention can be prepared in a number of ways well known to those skilled in the art of organic synthesis. By way of example, compounds of the present invention can be synthesized using the methods described below, together with synthetic methods known in the art of synthetic organic chemistry, or variations thereon as appreciated by those skilled in the art. Preferred methods include but are not limited to those methods described below. Compounds of the present invention i.e. urea or thiourea derivatives (VI) can be synthesized by following the steps outlined in Scheme 1.

Intermediate III can be obtained by treating I with II in the presence of a base (eg: K₂CO₃, Cs₂CO₃, NR₁R₂R₃, NaOR, KOR) in an inert solvent such as N,N-dialkylformamide, N,N-dialkylacetamide, dialkylethers, cyclic ethers, DMSO, N-methyl-2-pyrrolidinone at temperatures ranging from −78° C. to 200° C. Isocyanates or isothiocyanates of V can be obtained by treating compound of IV with phosgene, thiophosgene, carbonyldiimidazole in an inert solvent such as benzene, toluene at temperatures ranging from −78° C. to 200° C. The compound of present invention VI can be obtained by treating intermediates III with V in an organic solvent at temperatures −78° C. to 200° C. Alternatively compound of VI can be prepared by treatment of intermediate VII with III in the presence of base such as triethylamine in an inert solvent such as chloroform at temperatures ranging from −78° C. to 200° C. Carbamates or thiocarbamates (X) of the present invention can be synthesized by following the steps outlined in Scheme 2.

The disclosures in this application of all articles and references, including patents, are incorporated herein by reference.

The invention is illustrated further by the following examples, which are not to be construed as limiting the invention in scope or spirit to the specific procedures described in them. Those having skill in the art will recognize that the starting materials may be varied and additional steps employed to produce compounds encompassed by the present inventions, as demonstrated by the following examples. In some cases, protection of certain reactive functionalities may be necessary to achieve some of the above transformations. In general, such need for protecting groups, as well as the conditions necessary to attach and remove such groups, will be apparent to those skilled in the art of organic synthesis.

EXAMPLES Example 1 (R)-4-(3-Chloro-pyridin-2-yl)-2-methyl-piperazine-1-carboxylic acid (4-sec-butyl-phenyl)-amide Part A Synthesis of (R)-1-(3-Chloro-pyridin-2-yl)-3-methyl-piperazine

Dissolve 2,3-dichloropyridine (8.5 g, 0.057 moles) and (R)-(−)-2-methylpiperazine (5.75 g, 0.057 moles) in N,N-dimethylacetamide (125.0 mL) under nitrogen atmosphere. Add anhydrous powdered K₂CO₃ (23.75 g, 0.172 moles) to this mixture and stir at 135-140° C. for 48 h. New spot noticed in TLC (5% MeOH/CHCl₃/1% NEt₃) along with absence of starting materials. Cool the reaction mixture to room temperature, dilute with water (400 mL), extract with EtOAc (3×200 mL) and wash the combined organic extract with brine (2×150 mL). Dry over MgSO₄, concentrate under vacuum to afford crude product (20.0 g) as orange yellow liquid. Distil the crude under high vacuum to afford pyridylpiperazine derivative as yellow viscous oil (10 g, bp 112-115° C./0.1 torr). NMR (CDCl₃): δ ..1.1-1.12 (d, 3H, J=1.6 Hz), 2.50-2.53 (t, 1H), 2.83-2.87 (m, 1H), 3.06-3.08 (m, 3H), 3.67-3.75 (m, 2H), 6.80-6.82 (dd, 1H), 7.56-7.58 (dd, 1H), 8.17-8.18 (dd, 1H).

Part B Synthesis of (4-sec-Butyl-phenyl)-carbamic acid phenyl ester

Dissolve 4-isobutylaniline (4.5 g, 0.03 moles) in pyridine (30 mL) under nitrogen at room temperature. Add drop wise phenyl chloroformate (3.75 mL, 0.03 moles) to the reaction mixture at room temperature. Stir the mixture for 3 days and new spot noticed in TLC (30% EtOAc/hexane). Evaporate the reaction mixture under vacuo, partition between EtOAc and water (200 mL), wash several times with brine, dry (MgSO₄) and concentrate in vacuo. Purify the crude by flash column chromatography on a silica gel using (10% EtOAc/hexanes) to afford white solid.

Part C Title Compound

Dissolve Part A material of Example 1 (212 mg, 1.0 mmole) with Part B material of Example 1 (269 mg, 1.0 mmole) in CHCl₃ (10 mL) under nitrogen at room temperature. Add triethylamine (202 mg, 2.0 mmol) to the mixture and reflux for 4 hours. Cool the reaction mixture to room temperature, wash with 2 N aq. NaOH, water and dry (MgSO₄). Evaporate the dried extract in vacuo and purify by flash column chromatography on a silica gel using CHCl₃ to afford white solid.

NMR (CDCl₃): δ .0.78-0.83.. (t, 3H), 1.19-1.22 (d, 3H, J=2.2 Hz), 1.43-1.45 (d, 3H, J=2.3 Hz), 1.51-1.61 (m, 2H), 2.51-2.58 (m, 1H), 2.92-3.05 (m, 2H), 3.41-3.50 (m, 1H), 3.73-3.94 (m, 3H), 4.35 (m, 1H), 6.33 (bs, 1H), 6.86-6.90 (dd, 1H), 7.09-7.13 (m, 2H), 7.26-7.30 (m, 2H), 7.60-7.63 (dd, 1H), 8.18-8.20 (dd, 1H).

Example 2 (R)-(−)-4-(3-Chloro-pyridin-2-yl)-2-methyl-piperazine-1-carboxylic acid (4-trifluoromethyl-phenyl)-amide

Dissolve Part A material of example 1 (0.2756 g, 1.3 mmoles) in toluene (1.5 mL) under nitrogen at room temperature. Add drop wise 4-trifluoromethylphenyl isocyanate (0.2431 g, 1.3 mmoles) dissolved in toluene (50 mL) to the mixture over a period of 30 mins and stir at room temperature for 3 hours. Evaporate the solvent from reaction mixture under vacuum to afford colorless oil. Crystallize the oil from 1:1 Et₂O/hexane (2.0 mL) to afford white solid.

NMR (CDCl₃): δ .1.45-1.47 (d, 3H, J=1.7 Hz), 2.97-3.01 (t, 1H), 3.06-3.10 (m, 1H), 3.47-3.50 (m, 1H), 3.75-3.85 (m, 2H), 3.92-3.95 (m, 1H), 4.37-4.38 (m, 1H), 6.59 (bs, 1H), 6.88-6.91 (dd, 1H), 7.52-7.56 (m, 4H), 7.61-7.63 (dd, 1H), 8.19-8.21 (dd, 1H).

Mass spectrum (ESI): 399.3 (M+H).

Analysis calcd. for C₁₈H₁₈ClF₃N₄O: C, 54.21; H, 4.55; Cl, 8.89; F, 14.29; N, 14.05. Found: C, 54.47; H, 4.36; Cl, 8.50; F, 14.99; N, 13.94

Example 3 (R)-3-Chloro-pyridin-2-yl)-2-methyl-piperazine-1-carboxylic acid 4-tert-butyl-phenyl ester Part A Synthesis of (R)-4-(3-Chloro-pyridin-2-yl)-2-methyl piperazine-1-carbonyl chloride

Dissolve Part A material of Example 1 (1.06 g, 5.0 mmole)) in CH₂Cl₂ (50 mL) and saturated NaHCO₃ (50 mL) under nitrogen at room temperature. Add drop wise 20% COCl₂ in toluene (5.0 mL) at room temperature and stir overnight. Separate the organic layer, extract the aq. layer with CH₂Cl₂ (2×15 mL) and dry (MgSO₄). Evaporate the organic layer under vacuo to afford yellow oil.

Part B Title Compound

Dissolve Part A material of Example 3 (136 g, 0.5 mmole)) in pyridine (2.0 mL) under nitrogen at room temperature. Add 4-tert. butylphenol to the reaction mixture at room temperature and stir overnight. Evaporate the reaction mixture under vacuo, partition between water/CH₂Cl₂ (20 mL) and dry (MgSO₄). Evaporate the organic layer under vacuo and purify by flash column chromatography on silica gel using 15% EtOAc/hexane to afford colorless oil.

NMR (CDCl₃): δ .1.28-1.31 (3 S, 9H), 1.35-1.48 (m, 3H), 2.96-3.11 (m, 2H), 3.49 (m, 1H), 3.72-3.80 (m, 2H), 4.13-4.24 (m, 1H), 4.55-4.60 (m, 1H), 6.74-6.92 (m, 2H), 7.04-7.07 (m, 1H), 7.23-7.26 (m, 1H), 7.36-7.38 (m, 1H), 7.61-7.64 (m, 1H), 8.19-8.22 (m, 1H).

Mass spectrum (ESI): 388.2 (M+H).

Example 4 2-Methyl-4-(3-trifluoromethyl-pyridin-2-yl)-piperazine-1-carboxylic acid [4-(2,2,2-trifluoro-1-methyl-ethyl)-phenyl]-amide Part A Synthesis of 3-Methyl-1-(3-trifluoromethyl-pyridin-2-yl)-piperazine

Dissolve 2-chloro-3-trifluoromethylpyridine (5.4 g, 0.03 moles) and (R)-(−)-2-methylpiperazine (3.0 g, 0.03 moles) in N,N-dimethylacetamide (100.0 mL) under nitrogen atmosphere. Add anhydrous powdered K₂CO₃ (12.4 g, 0.09 moles) to this mixture and stir at 135-140° C. for 24 h. New spot noticed in TLC (5% MeOH/CHCl₃/1% NEt₃) along with absence of starting materials. Cool the reaction mixture to room temperature, dilute with water (300 mL), extract with EtOAc (3×200 mL) and wash the combined organic extract with brine (2×150 mL). Dry over MgSO₄, concentrate under vacuum to afford crude product as orange yellow liquid. Purify by flash column chromatography using 1% MeOH/CHCl₃ to afford yellow viscous oil.

Part B Synthesis of 4-(1-Trifluoromethyl-vinyl)-phenylamine

Dissolve 4-(4,4,5,5-tetramethyl-1,2,3-dioxaborolan-2-yl)aniline (2.19 g, 0.01 moles) and 2-Bromo-3,3,3-trifluoro-propene (2.61 g, 0.015 moles) in 1:1 THF/1,2-dimethoxyethane (30 mL) and cooled in an ice bath under nitrogen atmosphere. Add PdCl₂[(PPh₃)₂] (210 mg, 3 mol %) and AsPh₃ (459 mg, 15 mol %) to the reaction mixture followed by dropwise addition of 2.0 N Aq. NaOH (20 mL). Stirred the resultant mixture at room temp for 1 h followed by 70° C. for 15 h. Add additional 1.5 eq. of 2-Bromo-3,3,3-trifluoro-propene (2.61 g) to the reaction mixture and continued at 70° C. for 6 h. Evaporate the reaction mixture under vacuo, dissolve the residue in water/EtOAc (100 mL each), separate the organic layer, extract the aq. layer with EtOAc (2×100 mL), combine the organic layers and dry with MgSO4. Filter the dried extract, evaporate under vacuo and purify the crude by flash column chromatography on a silica gel using CHCl₃ to afford yellow oil.

Part C Synthesis of 1-Isocyanato-4-(1-trifluoromethyl-vinyl)-benzene

Cool 20% phosgene in toluene (5.0 mL) to −40° C. under N2 atmosphere. Dissolve Part B material of Example 4 (0.47 g, 2.5 mmoles) in toluene and add dropwise to the cooled stirred solution. Stir at −40° C. for 30 mins followed by room temperature for 1 h and then at reflux for 1 h. Concentrate in vacuo to afford orange yellow liquid.

Part D Synthesis of 2-Methyl-4-(3-trifluoromethyl-pyridin-2-yl)-piperazine-1-carboxylic acid [4-(1-trifluoromethyl-vinyl)-phenyl]-amide

Dissolve Part A material of example 4 (0.123 g, 0.5 mmoles) in toluene (1.0 mL) under nitrogen at room temperature. Add drop wise Part C material of Example 4 (0.106 g, 0.5 mmoles) dissolved in toluene (1.0 mL) to the mixture over a period of 5 mins and stir at room temperature for 20 hours. Evaporate the solvent from reaction mixture under vacuum and purify by flash column chromatography using CHCl₃ to afford yellow oil.

Part E Title Compound

Dissolve Part D material of example 4 (0.120 g, 0.262 mmoles) in EtOH (25.0 mL) at room temperature. Add 5% Pd/C (30 mg) and hydrogenate at 5 atm. of H₂ for 5 hours at room temperature. Filter the catalyst, evaporate the solvent from reaction mixture under vacuum and purify by PTLC using 5% MeOH/CHCl₃ to afford yellow oil.

NMR (CDCl₃): δ.1.38-1.41 (d, 3H), 1.45-1.47 (d, 3H), 3.05-3.11 (m, 1H), 3.22-3.62 (m, 4H), 3.82-3.90 (m, 1H), 4.35-4.42 (m, 1H, 6.40 (s, 1H), 7.05-7.10 (m, 1H), 7.21-7.40 (m, 5H), 7.95-7.97 (d, 1H), 8.42-8.46 (d, 1H).

Mass spectrum (ESI): 461.3 (M+N).

Example 5 4-(3-Chloro-pyridin-2-yl)-2-methyl-piperazine-1-carboxylic acid [4-(2,2,2-trifluoro-1-methyl-ethyl)-phenyl]-amide Part A Synthesis of 4-(2,2,2-Trifluoro-1-methyl-ethyl)-phenylamine

Dissolve Part B material of example 4 (0.375 g, 0.262 mmoles) in MeOH (25.0 mL) at room temperature. Add raney Ni (500 mg) and hydrogenate at 40 atm. of H₂ for 20 hours at room temperature. Filter the catalyst, evaporate the solvent from reaction mixture under vacuum and purify by flash column chromatography using CHCl₃ to afford yellow oil.

Part B Synthesis of 1-Isocyanato-4-(2,2,2-trifluoro-1-methyl-ethyl)-benzene

Cool 20% phosgene in toluene (2.0 mL) to −40° C. under N2 atmosphere. Dissolve Part A material of Example 5 (0.139 g, 1.0 mmole) in toluene and add drop wise to the cooled stirred solution. Stir at −40° C. for 30 mins followed by room temperature for 3 h and then at reflux for 18 h. Concentrate in vacuo to afford yellow liquid.

Part C Title Compound

Dissolve Part A material of example 1 (0.169 g, 0.795 mmoles) in toluene (1.0 mL) under nitrogen at room temperature. Add drop wise Part B material of Example 5 (0.171 g, 0.795 mmoles) dissolved in toluene (1.0 mL) to the mixture over a period of 5 mins and stir at room temperature for 20 hours. Evaporate the solvent from reaction mixture under vacuum and purify by PTLC using 5% MeOH/CHCl₃ to afford white amorphous powder.

NMR (CDCl₃): δ .1.44-1.49 (2d, 6H), 2.94-3.11 (m, 2H), 3.36-3.51 (m, 2H), 3.74-3.94 (m, 3H), 4.35-4.37 (m, 1H), 6.41 (s, 1H), 6.87-6.90 (dd, 1H), 7.23-7.26 (m, 2H), 7.36-7.38 (m, 2H), 7.60-7.63 (dd, 1H), 8.19-8.20 (dd, 1H).

Mass spectrum (ESI): 427.3 (M+H).

Example 6 (R)-4-(3-Chloro-pyridin-2-yl)-2-methyl-piperazine-1-carboxylic acid [4-(1,2,2,2-tetrafluoro-1-trifluoromethyl-1-ethyl)-phenlyl]-amide Part A Synthesis of 1-Isocyanato-4-(1,2,2,2-tetrafluoro-1-trifluoromethyl-ethyl)-benzene

Cool 20% phosgene in toluene (20.0 mL) to 40° C. under N2 atmosphere. Dissolve 4-heptafluoroisopropylaniline (2.0 g, 7.7 mmoles; see: EP 1006102 for aniline preparation) in toluene (5.0 mL) and add drop wise to the cooled stirred solution. Stir at −40° C. for 30 mins followed by room temperature for 2 h and then at reflux for 4 h. Concentrate in vacuo to afford yellow liquid.

Part B Title Compound

Dissolve Part A material of example 1 (0.106 g, 0.795 mmoles) in toluene (1.0 mL) under nitrogen at room temperature. Add drop wise Part A material of Example 6 (0.144 g, 0.5 mmoles) dissolved in toluene (1.0 mL) to the mixture over a period of 5 mins and stir at room temperature for 20 hours. Evaporate the solvent from reaction mixture under vacuum and purify by PTLC using 5% MeOH/CHCl₃ to afford white amorphous powder.

NMR (CDCl₃): δ .1.44-1.46 (d, 3H, J=1.6 Hz), 2.93-3.10 (m, 2H), 3.45-3.52 (m, 1H), 3.74-3.78 (m, 2H), 3.91-3.94 (m, 1H), 4.37-4.38 (m, 1H), 6.60 (s, 1H), 6.87-6.90 (dd, 1H), 7.52-7.60 (m, 4H), 7.61-7.63 (m, 1H), 8.18-8.20 (dd, 1H).

Mass spectrum (ESI): 499.2 (M+H).

Example 7 4-(3-Chloro-pyridin-2-yl)-2-methyl-piperazine-1-carbothioic acid (4-isopropyl-phenyl)-amide

Dissolve Part A material of example 1 (0.212 g, 1.0 mmoles) in toluene (1.0 mL) under nitrogen at room temperature. Add drop wise 4-isopropylisothiocyanate (0.177 g, 0.5 mmoles) dissolved in toluene (1.0 mL) to the mixture over a period of 5 mins and stir at room temperature for 20 hours. Evaporate the solvent from reaction mixture under vacuum and purify by flash column chromatography using CHCl₃ to afford white solid (mp 49-51° C.).

NMR (CDCl₃): δ .1.22-1.25 (d, 3H), 1.41-1.43 (d, 3H), 2.80-3.20 (m, 3H), 3.45-3.60 (m, 1H), 3.65-3.80 (m, 2H), 4.35-4.39 (m, 1H), 5.05-5.20 (m, 1H), 6.85-6.90 (s, 1H), 7.15-7.35 (m, 5H), 7.42-7.44 (d, 1H), 8.18-8.20 (d, 1H).

Mass spectrum (ESI): 387.2 (M+H).

Example 8 Synthesis of 4-(3-Trifluoromethyl-2-pyridinyl)-N-(3-methoxy-4-hydroxyphenylmethyl)-1-piperazinecarboxamide

A quantity of 0.2 mL of a 0.2 M isocyante solution in dichloroethane is treated with 0.26 mL of a 0.2 mL solution of piperazine in 95:5 toluene:N-Methyl Morphine at 60° C. for 16 hr. The resulting reaction solution was cooled to room temperature. To the resulting solution is added 1 drop of amino propyl morpholine and warmed to 60° C. for an additional hour. The resulting mixture is cooled to room temperature and chromatographed SiO₂ with ethyl acetate to afford 10 mg 63% of the title compound (Compound 1). MS m/z 410.16 found: 411, 433 Na adduct. Capsaicin receptor K_(i): 366 nM

Example 9 Additional Compounds

Using variations of the methods given in Schemes 1 and 2, and Examples 1-8 that will be readily apparent to one skilled in the art of organic synthesis the compounds list in Tables II, III and IV are prepared. Commercial grade reagents are used without further purification in the preparation of these compound

TABLE II

Compound R R1 R2 A X Calc Found Activity Chemical Name 2 4-Butyl H H NH 3-NO2 383 384, * 4-(3-Nitro-2-pyridinyl)-N-[4-(n- 406 Na butyl)phenyl]-1-piperazinecarboxamide adduct 3 4-Butyl H H NH 3-CF3 406 407, * 4-(3-Trifluoromethyl-2-pyridinyl)-N-[4- 429 Na (n-butyl)phenyl]-1-piperazinecarboxamide adduct 4 4- H H NH 3-Me 338 339, * 4-(3-Methyl-2-pyridinyl)-N-[4- Isopropyl 361 Na (isopropyl)phenyl]-1- adduct Piperazinecarboxamide 5 4-Butyl H H NH 3-Me 352 353, NA 4-(3-Methyl-2-pyridinyl)-N-[4-(n- 375 Na butyl)phenyl]-1-piperazinecarboxamide adduct 6 4- H H NH 3-CF3 352 353, * 4-(3-Trifluoromethyl-2-pyridinyl)-N-[4- Isopropyl 375 Na (isopropyl)phenyl]-1- adduct piperazinecarboxamide 7 4- H H NH 3-Cl, 5- 427 427, * 4-(3-Chloro-5-trifluoromethyl-2- Isopropyl CF3 449 Na pyridinyl)-N-[4-(isopropyl)phenyl]-1- adduct piperazinecarboxamide 8 4- H H NH 3-Cl 359 359, 4-(3-Chloro-2-pyridinyl)-N-[4- Isopropyl 381 Na (isopropyl)phenyl]-1- adduct piperazinecarboxamide 9 4- H H NH 3,5- 393 393, 4-(3,5-Dichloro-2-pyridinyl)-N-[4- Isopropyl diCl 415 Na (isopropyl)phenyl]-1- adduct piperazinecarboxamide 10 4- H H CH═CH 3-CF3 * 1-(3-Methyl-2-pyridinyl)-3-(4- Isopropyl trifluoromethyl phenyl)-prop-2-en-1-one 11 4-CF3 H H CH═CH 3-Me * 1-(3-Trifluoromethyl-2-pyrindinyl)-3-(4- isopropylphenyl)-prop-2-en-1-one 12 4- H H NH 3-CN 349 * 4-(3-Cyano-2-pyridinyl)-N-[4- Isopropyl (isopropyl)phenyl]-1- piperazinecarboxamide 13 4- Me H NH 3-Cl 373 373, NA 4-(3-Chloro-2-pyridinyl)-N-[4- Isopropyl 395 Na (isopropyl)phenyl]-2-methyl-1- adduct piperazinecarboxamide 14 4- R-Me H NH 3-Cl 373 373, * 4-(3-Chloro-2-pyridinyl)-N-[4- Isopropyl 395 Na (isopropyl)phenyl]-1- adduct piperazinecarboxamide 15 4- S-Me H NH 3-Cl 373 373, NA 4-(3-Chloro-2-pyridinyl)-N-[4- Isopropyl 395 Na (isopropyl)phenyl]-2-methylthio-1- adduct piperazinecarboxamide 16 4-CF3 H H NH 3,5- 373 NA 4-(3,5-Dichloro-2-pyridinyl)-N-[4 diCl (isopropyl)phenyl]-1- piperazinecarboxamide * indicates a Ki value of less than 4 uM in a Capsaicin receptor binding assay A Capsaicin receptor binding assay is described in example 10 NA = Not available Mass spec data are collected using a MicroMass 60 series (Beverly, MA) LC-MS TOF spectrometer in the electrospray mode. LC conditions: YMC-pack pro C18 column, 33 × 4.6 ID, Particle size: S-5 μm 120 A, supplied by WATERS, Milford, MA, 95%-5% gradient, 2 min gradient time, flow rate 3.5 ml/min, Mobile Phase: A: 0.05% TFA in H2O/MeOH (95:5 v/v) B: 0.05% TFA IN MeOH/H2O (95:5 v/v), 1 ul injection volume.

TABLE III Cmp. # STRUCTURE IUPAC Name EC50 17

N-(4-tert-butylphenyl)-4-(3-chloropyridin-2-yl)piperazine-1-carboxamide * 18

(2R)-4-(3-chloropyridin-2-yl)-N-(4-cyclohexylphenyl)-2-methylpiperazine-1-carboxamide * 19

(2R)-4-(3-chloropyridin-2-yl)-N-[2-chloro-4-(trifluoromethyl)phenyl]-2-methylpiperazine-1-carboxamide 20

(2R)-4-(3-chloropyridin-2-yl)-2-methyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide * 21

(2R)-N-(4-tert-butylphenyl)-4-(3-chloropyridin-2-yl)-2-methylpiperazine-1-carboxamide * 22

(2R)-4-(3-chloropyridin-2-yl)-N-(4-isopropylphenyl)-2-methylpiperazine-1-carboxamide * 23

(2S)-4-(3-chloropyridin-2-yl)-N-(4-trifluoromethylphenyl)-2-methylpiperazine-1-carboxamide * 24

(2S)-N-(4-tert-butylphenyl)-4-(3-[chloropyridin-2-yl)-2-methylpiperazine-1-carboxamide * 25

(2S)-4-(3-chloropyridin-2-yl)-N-(4-isopropylphenyl)-2-methylpiperazine-1-carboxamide * 26

(2R)-4-(3-chloropyridin-2-yl)-2-methyl-N-(4-piperidin-1-ylphenyl)piperazine-1-carboxamide * 27

(2S)-4-(3-chloropyridin-2-yl)-N-[2-fluoro-4-(trifluoromethyl)phenyl]-2-methylpiperazine-1-carboxamide * 28

(2R)-2-methyl-N-[4-(trifluoromethyl)phenyl]-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 29

(2R)-N-(4-tert-butylphenyl)-2-methyl-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 30

(2R)-N-(4-isopropylphenyl)-2-methyl-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 31

4-(3-chloropyridin-2-yl)-2,6-dimethyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide * 32

N-(4-tert-butylphenyl)-4-(3-chloropyridin-2-yl)-2,6-dimethylpiperazine-1-carboxamide * 33

4-(3-chloropyridin-2-yl)-N-(4-isopropylphenyl)-2,6-dimethylpiperazine-1-carboxamide * 34

(2R)-N-(4-cyclohexylphenyl)-2-methyl-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 35

4-(3-chloropyridin-2-yl)-N-(4-cyclohexylphenyl)-2,6-dimethylpiperazine-1-carboxamide * 36

(2R)-4-(3-chloropyridin-2-yl)-N-(4cyclopentylphenyl)-2-methylpiperazine-1-carboxamide * 37

(2R)-N-(4-cyclopentylphenyl)-2-methyl-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 38

(2R)-4-isoquinolin-1-yl-2-methyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide * 39

(2R)-N-(4-tert-butylphenyl)-4-isoquinolin-1-yl-2-methylpiperazine-1-carboxamide * 40

(2R)-N-(4-isopropylphenyl)-4-isoquinolin-1-yl-2-methylpiperazine-1-carboxamide * 41

(2R)-N-(4-cyclopentylphenyl)-4-isoquinolin-1-yl-2-methylpiperazine-1-carboxamide * 42

(2R)-N-(4-cyclohexylphenyl)-4-isoquinolin-1-yl-2-methylpiperazine-1-carboxamide * 43

(2R)-N-(4-tert-butylphenyl)-4-[3-(dimethylamino)pyridin-2-yl]-2-methylpiperazine-1-carboxamide * 44

(2R)-4-[3-(dimethylamino)pyridin-2-yl]-2-methyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide * 45

(2R)-N-(4-tert-butylphenyl)-4-(3-methoxypyridin-2-yl)-2-methylpiperazine-1-carboxamide * 46

(2R)-4-(3-methoxypyridin-2-yl)-2-methyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide 47

(2R)-N-[4-cyclohexylphenyl)-4-(3-methoxypyridin-2-yl)-2-methylpiperazine-1-carboxamide * 48

(2R)-4-(3-chloropyridin-2-yl)-N-[4-(3,6-dihydro-2H-pyran-4-yl)phenyl]-2-methylpiperazine-1-carboxamide * 49

(2R)-4-(3-chloropyridin-2-yl)-2-methyl-N-(4-tetrahydro-2H-pyran-4-ylphenyl)piperazine-1-carboxamide * 50

(2R)-4-(3-chloropyridin-2-yl)-N-[4-(4-hydroxyretrahydro-2H-pyran-4-yl)phenyl]-2-methylpiperazine-1-carboxamide * 51

(2R)-N-[4-(4-hydroxytetrahydro-2H-pyran-4-yl)phenyl]-2-methyl-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 52

(2R)-4-(3-chloropyridin-2-yl)-2-methyl-N-[4-(2-methyl-1,3-thiazol-4-yl)phenyl]piperazine-1-carboxamide * 53

(2R)-4-(3-chloropyridin-2-yl)-N-[4-(2-ethyl-1,3-thiazol-4-yl)phenyl]-2-methylpiperazine-1-carboxamide * 54

(2R)-4-(3-chloropyridin-2-yl)-N-[4-(2-methoxy-1,1-dimethylethyl)phenyl]-2-methylpiperazine-1-carboxamide * 55

(2R)-N-[4-(2-methoxy-1,1-dimethylethyl)phenyl]-2-methyl-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 56

(2R)-4-(3-chloropyridin-2-yl)-N-[4-(1-cyano-3-methylethyl)phenyl]-2-methylpiperazine-1-carboxamide * 57

(2R)-N-[4-(1-cyano-1-methylethyl)phenyl]-2-methyl-4-[3-(trif1uoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 58

N-(4-tert-butylphenyl)-4-(3-chloropyridin-2-yl)-2-ethylpiperazine-1-carbaxamide * 59

4-(3-chloropyridin-2-yl)-2-ethyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide * 60

4-(3-chloropyridin-2-yl)-2-ethyl-N-(4-isopropylphenyl)piperazine-1-carboxamide * 61

N-(4-tert-butylphenyl)-2-ethyl-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 62

2-ethyl-N-[4-(trifluoromethyl)phenyl]-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 63

2-ethyl-N-(4-isopropylphenyl)-4-[3-(trifluoromethyl)pyridin-2-yl]-piperazine-1-carboxamide * 64

2-tert-butyl-N-(4-tert-butylphenyl)-4-(3-chloropyridin-2-yl)piperazine-1-carboxamade * 65

2-tert-butyl-4-(3-chloropyridin-2-yl)-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide 66

2-tert-butyl-4-(3-chloropyridin-2-yl)-N-[4-isopropylphenyl)piperazine1-carboxamide 67

2-tert-butyl-N-(4-tert-butylphenyl)-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide 68

2-tert-butyl-N-[4-(trifluoromethyl)phenyl)-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 69

N-(4-tert-butylphenyl)-4-(3-chloropyridin-2-yl)-2-isopropylpiperazine-1-carboxamide * 70

4-(3-chloropyridin-2-yl)-2-isopropyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide 71

4-(3-chloropyridin-2-yl)-2-isopropyl-N-(4-isopropylphenyl)piperazine-1-carboxamide 72

N-(4-tert-butylphenyl)-2-isopropyl-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 73

2-isopropyl-N-[4-(trifluoromethyl)phenyl]-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 74

2-isopropyl-N-(4-isopropylphenyl)-4-[3-(trifluoromethyl)pyridin-2-yl]-piperazine-1-carboxamide * 75

(2R)-4-(3-fluoropyridin-2-yl)-2-methyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide * 76

(2R)-N-(4-tert-butylphenyl)-4-(3-fluoropyridin-2-yl)-2-methylpiperazine-1-carboxamide * 77

(2R)-4-(3-fluoropyridin-2-yl)-N-(4-isopropylphenyl)-2-methylpiperazine-1-carboxamide * 78

(2R)-N-(4-cyclohexylphenyl)-4-(3-fluoropyridin-2-yl)-2-methylpiperazine-1-carboxamide * 79

(2R)-N-(4-cyclopentylphenyl)-4-(3-fluoropyridin-2-yl)-2-methylpiperazine-1-carboxamide * 80

N-(4-chlorophenyl)-4-(6-chloropyridin-2-yl)piperazine-1-carboxamide 81

4-(6-chloropyridin-2-yl)-N-phenylpiperazine-1-carboxamide 82

(2R)-N-(4-tert-butylphenyl)-4-(3-cyanopyridin-2-yl)-2-methylpiperazine-1-carboxamide * 83

(2R)-4-(3-cyanopyridin-2-yl)-2-methyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide * 84

(2R)-2-methyl-4-(6-methylpyridin-2-yl)-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide 85

(2R)-4-(6-methoxypyridin-2-yl)-2-methyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide 86

(2R)-N-(4-tert-butylphenyl)-2-methyl-4-(6-methylpyridin-2-yl)-piperazine-1-carboxamide * 87

(2R)-N-(4-tert-butylphenyl)-4-(6-methoxypyridin-2-yl)-2-methylpiperazine-1-carboxamide 88

(2R)-N-(4-isopropylphenyl)-2-methyl-4-(6-methylpyridin-2-yl)piperazine-1-carboxamide 89

(2R)-N-(4-isopropylphenyl)-4-(6-methoxypyridin-2-yl)-2-methylpiperazine-1-carboxamide 90

(2R)-N-(4-cyclopentylphenyl)-2-methyl-4-(6-methylpyridin-2-yl)piperazine-1-carboxamide 91

(2R)-N-(4-cyclopentylphenyl)-4-(6-methoxypyridin-2-yl)-2-methylpiperazine-1-carboxamide

TABLE IV Cpd. # STRUCTURE IUPAC Name EC50 93

4-(3-chloropyridin-2-yl)-N-[5-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 94

(2R)-4-(3-chloropyridin-2-yl)-2-methyl-N-[5-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 95

(2R)-N-(4-tert-butylphenyl)-4-(3-chloropyrazin-2-yl)-2-methylpiperazine-1-carboxamide * 96

(2R)-4-(3-chloropyrazin-2-yl)-N-(4-isopropylphenyl)-2-methylpiperazine-1-carboxamide * 97

(2R)-4-(3-chloropyrazin-2-yl)-2-methyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide * 98

(2R)-4-(3-chloropyridin-2-yl)-2-methyl-N-[6-(trifluoromethyl)pyridin-3-yl]piperazine-1-carboxamide * 99

(2R)-N-(4-tert-butylcyclohexyl)-4-(3-chloropyridin-2-yl)-2-methylpiperazine-1-carboxamide * 100

(2R)-4-(3-chloropyridin-2-yl)-N-(4-isopropylcyclohexyl)-2-methylpiperazine-1-carboxamide * 101

(2R)-N-(4-isopropylcyclohexyl)-2-methyl-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 102

(2R)-4-isoquinolin-1-yl-2-methyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide 103

(2R)-N-(4-tert-butylphenyl)-4-isoquinolin-1-yl-2-methylpiperazine-1-carboxamide 104

(2R)-N-(4-isopropylphenyl)-4-isoquinolin-1-yl-2-methylpiperazine-1-carboxamide 105

(2R)-N-(4-cyclopentylphenyl)-4-isoquinolin-1-yl-2-methylpiperazine-1-carboxamide 106

(2R)-N-(4-cyclohexylphenyl)-4-isoquinolin-1-yl-2-methylpiperazine-1-carboxamide

TABLE V Cmp # Structure Name EC50 107

N-(4-chlorophenyl)-4-[4-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 108

N-[4-(trifluoromethoxy)phenyl]-4-[4-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 109

N-(3-chlorophenyl)-4-[4-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 110

N-[3-(trifluoromethyl)phenyl]-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 111

N-(4-methylphenyl)-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide 112

N-(3-bromophenyl)-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide 113

N-(3-methoxyphenyl)-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 114

4-(5-nitropyridin-2-yl)-N-[4-(trifluoromethoxy)phenyl]piperazine-1-carboxamide 115

N-(1-naphthyl)-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide 116

N-(3-nitrophenyl)-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 117

N-[4-(trifluoromethoxy)phenyl]-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 118

N-(4-chloro-3-nitrophenyl)-4-[3-(trifiuoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 119

N-(3,5-dichlorophenyl)-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 120

(2R)-4-(3-chloropyridin-2-yl)-N-{4-[cyano(phenyl)methyl]phenyl}-2-methylpiperazine-1-carboxamide * 121

(2R)-4-(3-chloropyridin-2-yl)-2-methyl-N-[3-methyl-4-(trifluoromethyl)phenyl]piperazine-1-carboxamide * 122

(2R)-4-(3-fluoropyridin-2-yl)-2-methyl-N-[3-methyl-4-(trifluoromethyl)phenyl]piperazine-1-carboxamide * 123

(2R)-4-{3-[bis(methylsulfonyl)amino]pyridin-2-yl}-N-(4-tert-butylphenyl)-2-methylpiperazine-1-carboxamide * 124

(2R)-2-methyl-N-[3-methyl-4-(trifluoromethyl)phenyl]-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 125

(2R)-4-(3-chloropyridin-2-yl)-2-methyl-N-{4-[1-(trifluoromethyl)vinyl]phenyl}piperazine-1-carboxamide * 126

(2R)-2-methyl-4-[3-(trifluoromethyl)pyridin-2-yl]-N-{4-[1-(trifluoromethyl)vinyl]phenyl}piperazine-1-carboxamide * 127

(2R)-4-(3-fluoropyridin-2-yl)-2-methyl-N-{4-[1-(trifluoromethyl)vinyl]phenyl}piperazine-1-carboxamide * 128

(2R)-N-(4-sec-butylphenyl)-4-(3-fluoropyridin-2-yl)-2-methylpiperazine-1-carboxamide * 129

(2R)-2-methyl-N-[4-(2,2,2-trifluoro-1-methylethyl)phenyl]-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 130

(2R)-4-(3-fluoropyridin-2-yl)-2-methyl-N-[4-(2,2,2-trifluoro-1-methylethyl)phenyl]piperazine-1-carboxamide * 131

(2R)-4-(3-chloro-5-nitropyridin-2-yl)-2-methyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide * 132

(2R)-4-(5-amino-3-chloropyridin-2-yl)-2-methyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide * 133

(2R)-4-(3-fluoropyridin-2-yl)-N-[3-fluoro-4-(trifluoromethyl)phenyl]-2-methylpiperazine-1-carboxamide * 134

(2R)-N-[3-fluoro-4-(trifluoromethyl)phenyl]-2-methyl-4-[3-trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 135

(2R)-4-(3-chloropyridin-2-yl)-2-methyl-N-[4-(2,2,2-trifluoro-1-methylethyl)phenyl]piperazine-1-carboxamide * 136

(2R)-4-(3-chloropyridin-2-yl)-2-methyl-N-(2,2,4,4-tetrafluoro-4H-1,3-benzodioxin-6-yl)piperazine-1-carboxamide * 137

(2R)-4-(3-fluoropyridin-2-yl)-2-methyl-N-(2,2,4,4-tetrafluoro-4H-1,3-benzodioxin-6-yl)piperazine-1-carboxamide * 138

(2R)-2-methyl-N-(2,2,4,4-tetrafluoro-4H-1,3-benzodioxin-6-yl)-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 139

(2R)-4-[3-(aminosulfonyl)pyridin-2-yl]-N-(4-tert-butylphenyl)-2-methylpiperazine-1-carboxamide * 140

(2R)-N-(4-benzoylphenyl)-4-(3-chloropyridin-2-yl)-2-methylpiperazine-1-carboxamide * 141

(2R)-4-(3-chloropyridin-2-yl)-N-(4-iodophenyl)-2-methylpiperazine-1-carboxamide * 142

(2R)-4-(3-chloropyridin-2-yl)-N-(9H-fluoren-2-yl)-2-methylpiperazine-1-carboxamide * 143

(2R)-N-(9H-fluoren-2-yl)-2-methyl-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 144

(2R)-4-[3-cyano-6-(trifluoromethyl)pyridin-2-yl]-2-methyl-N-[4-(trifluoromethyl)phenyl]piperazine-1-carboxamide 145

(2R)-N-(4-tert-butylphenyl)-4-[3-cyano-6-(trifluoromethyl)pyridin-2-yl]-2-methylpiperazine-1-carboxamide 146

(2R)-4-[3-cyano-6-(trifluoromethyl)pyridin-2-yl]-N-(4-cyclopentylphenyl)-2-methylpiperazine-1-carboxamide 147

(2R)-4-[3-cyano-6-(trifluoromethyl)pyridin-2-yl]-N-(4-cyclohexylphenyl)-2-methylpiperazine-1-carboxamide 148

(2R)-4-(3-chloropyridin-2-yl)-2-methyl-N-{4-[2,2,2-trifluoro-1,1-bis(trifluoromethyl)ethyl]phenyl}piperazine-1-carboxamide * 149

(2R)-2-methyl-N-{4-[2,2,2-trifluoro-1,1-bis(trifluoromethyl)ethyl]phenyl}-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 150

(2R)-4-(3-chloropyridin-2-yl)-N-(3-iodophenyl)-2-methylpiperazine-1-carboxamide * 151

(2R)-4-(3-fluoropyridin-2-yl)-N-(3-iodophenyl)-2-methylpiperazine-1-carboxamide * 152

(2R)-N-(4-butylphenyl)-4-(3-chloropyridin-2-yl)-2-methylpiperazine-1-carboxamide * 153

2-(fluoromethyl)-N-[4-(trifluoromethyl)phenyl]-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 154

(2R)-4-(3-chloropyridin-2-yl)-2-methyl-N-[4-methyl-3-(trifluoromethyl)phenyl]piperazine-1-carboxamide * 155

(2R)-2-methyl-N-[4-methyl-3-(trifluoromethyl)phenyl]-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 156

(2R)-N-[4-bromo-3-(trifluoromethyl)phenyl]-4-(3-chloropyridin-2-yl)-2-methylpiperazine-1-carboxamide * 157

(2R)-N-[4-bromo-3-(trifluoromethyl)phenyl]-2-methyl-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 158

(2R)-4-(3-chloropyridin-2-yl)-N-[4-chloro-3-(trifluoromethyl)phenyl]-2-methylpiperazine-1-carboxamide * 159

(2R)-4-(3-chloropyridin-2-yl)-N-[4-fluoro-3-(trifluoromethyl)phenyl]-2-methylpiperazine-1-carboxamide * 160

(2R)-N-[4-chloro-3-(trifluoromethyl)phenyl]-2-methyl-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 161

(2R)-N-[4-fluoro-3-(trifluoromethyl)phenyl]-2-methyl-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide * 162

(2R)-4-(3-chloropyridin-2-yl)-2-methyl-N-{4-[1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl]phenyl}piperazine-1-carboxamide * 163

(2R)-2-methyl-N-{4-[1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl]phenyl}-4-[3-(trifluoromethyl)pyridin-2-yl]piperazine-1-carboxamide *

TABLE VI Cmp. # Structure NAME EC50 164

(2R)-4-(3-chloropyrazin-2-yl)-2-methyl-N-{4-[1,2,2,2-tetrafluoro-1-(trifluoromethyl)ethyl]phenyl}piperazine-1-carboxamide * 165

(2R)-4-(3-chloropyrazin-2-yl)-2-methyl-N-{4-cyclopentyl-phenyl}piperazine-1-carboxamide * 166

(2R)-4-(3-chloropyrazin-2-yl)-2-methyl-N-{4-cyclohexyl-phenyl}piperazine-l-carboxamide * 167

* 168

* 169

* 170

* 171

* 172

* 173

* 174

* in Table III-Table VI indicates a EC50 value of less than 1 uM in an antagonist assay for Capsaicin receptor mediated calcium mobilization. An assay for Capsaicin receptor mediated calcium mobilization is described in example 11

Example 10 Capsaicin Receptor Binding Assay

The following assay is a standard assay of capsaicin receptor binding that may be used to determine the binding affinity of compounds for the capsaicin (VR1) receptor.

Materials. [³H]Resiniferatoxin (RTX, 37 Ci/mmol) was synthesized by and obtained from the Chemical Synthesis and Analysis Laboratory, National Cancer Institute-Frederick Cancer Research and Development Center, Frederick, Md. [³H] RTX may also be obtained from commercial vendors, e.g., Amersham Pharmacia Biotech, Inc. 800 Centennial Avenue, P.O. Box 1327, Piscataway, N.J. 08855 (code TRK 1069). Nonradioactive RTX may be purchased from Alexis Corp. (San Diego, Calif.) and capsazepine from RBI (Natick, Mass.).

Molecular Biology

A cDNA encoding the full length human capsaicin receptor (SEQ ID NO:1 or SEQ ID NO:2) is subcloned in the appropriate orientation for expression into an expression vector such as pcDNA3.1 (Invitrogen, Carlsbad, Calif.) or pUHG102-3 (Clontech, Palo Alto, Calif.) for recombinant expression in mammalian cells.

Cell Culture. Human embryonic kidney (HEK293) cells are transfected with a pcDNA3.1 expression construct encoding the full length human capsaicin receptor (i.e. containing either the nucleotide sequence of SEQ ID NO:1 and SEQ ID NO:2) using standard methods. These transfected cells are selected for two weeks in media containing G418 (400 ug/ml) and then maintained as a pool of stably transfected cells.

pUHG102 VR1 expression plasmids are transfected into Chinese Hamster Ovary (CHO) cells containing the pTet Off Regulator plasmid (Clontech). In these cells, expression of the pUHG plasmid is repressed in the presence of tetracycline but is induced upon removal of the antibiotic. Stable clones are isolated in culture medium containing puromycin (10 ug/ml) and maintained in medium supplemented with tetracycline (1 ug/ml). Cells utilized for assays are grown in culture medium without antibiotic for 48-72 hours prior to use. For radioligand binding experiments, cells are seeded in T175 cell culture flasks in media without antibiotics and grown to approximately 90% confluency. The flasks are then washed with PBS and harvested in PBS containing 5 mM EDTA. The cells are pelleted by gentle centrifugation and stored at −80° C. until assayed.

Membrane Preparations

Previously frozen cells are disrupted with the aid of a tissue homogenizer in ice-cold HEPES homogenization buffer (5 mM KCl 5, 5.8 mM NaCl, 0.75 mM CaCl₂, 2 mM MgCl₂, 320 mM sucrose, and 10 mM HEPES pH 7.4), Tissue homogenates are first centrifuged for 10 min at 1000×g (4° C.) to remove the nuclear fraction and debris and then the supernatant from the first centrifugation is further centrifuged for 30 min at 35,000×g (4° C.) to obtain a partially purified membrane fraction. Membranes are resuspended in the HEPES homogenization buffer prior to being assayed. An aliquot of this membrane homogenate is used to determine protein concentration via the Bradford method (BIO-RAD Protein Assay Kit, #500-0001, BIO-RAD, Hercules, Calif.).

Radioligand Binding

Binding studies with [³H]RTX are carried out essentially according to a published protocol (Szallasi and Blumberg, 1992, J. Pharmacol. Exp. Ter. 262: 883-888) in which non-specific RTX binding is reduced by adding bovine alpha₁ acid glycoprotein (100 ug per tube) after the binding reaction has been terminated. The homogenate is centrifuged as before and resuspended to a protein concentration of 333 ug/ml in homogenization buffer. Binding assay mixtures were set up on ice and contained [³H]RTX (specific activity 2200 mCi/ml), 2 ul non-radioactive ligands test compound, 0.25 mg/ml bovine serum albumin (Cohn fraction V), and 5×10⁴−1×10⁵ VR1-transfected cells. The final volume was adjusted to 500 ul (competition binding assays) or 1,000 ul (saturation binding assays) with the ice-cold HEPES homogenization buffer solution (pH 7.4) described above. Non-specific binding was defined as that occurring in the presence of 1 uM non-radioactive RTX. For saturation binding, [³H]RTX was added in the concentration range of 7-1,000 pM, using 1 to 2 dilutions. Typically 11 concentration points are collected per saturation binding curve.

Competition binding assays were performed in the presence of 60 pM [³H]RTX and various concentrations of competing ligands. The binding reactions are initiated by transferring the assay mixtures into a 37° C. water bath and are terminated following a 60 min incubation period by cooling the tubes on ice. Membrane-bound RTX is separated from free, as well as any alpha₁-acid glycoprotein-bound RTX, by filtration onto WALLAC glass fiber filters (PERKIN-ELMER, Gaithersburg, Md.) which are pre-soaked with 1.0% PEI (polyethyleneimine) for 2 hours prior to use. Filters are allowed to dry overnight then counted in a WALLAC 1205 BETA PLATE counter after addition of WALLAC BETA SCINT scintillation fluid.

Equilibrium binding parameters were determined by fitting the allosteric Hill equation to the measured values with the aid of the computer program FIT P (Biosoft, Ferguson, Mo.) as described previously (Szallasi, et al. (1993) J. Pharmacol. Exp. Ther. 266:678-683)).

Though compounds exhibiting K_(i) values for capsaicin receptors of greater than 1 uM are generally less preferred as pharmaceutical agents, useful compounds of the invention exhibit K_(i) values for capsaicin receptors of less than 4 uM, more preferred compounds exhibit K_(i) values of less than 1 uM, even more preferred compounds exhibit K_(i) values of less than 100 nM, more highly preferred compounds exhibit K_(i) values of less than 50 nM, even more highly preferred compounds exhibit K_(i) values of less than 25 nM and the most preferred compounds of the invention yield K_(i) values of less than or about equal to 10 nM in this assay.

Example 11 Calcium Mobilization Assay

The following assay can be used to monitor the response of cells capsaicin receptors to capsaicin and other vanilloid ligands of the capsaicin receptor. The assay can also be used to determine if test compounds act as agonists or antagonists of capsaicin receptors.

Cells transfected with expression plasmids (as described in Example 10) and thereby expressing the human capsaicin receptor are seeded and grown to 70-90% confluency in FALCON black-walled, clear-bottomed 96-well plates (#3904, BECTON-DICKINSON, Franklin Lakes, N.J.). The culture media are emptied from the 96 well plates and FLUO-3 AM calcium sensitive dye (Molecular Probes, Eugene, Oreg.) is added to each well (dye solution: 1 mg FLUO-3 AM, 440 uL DMSO and 440 ul 20% pluronic acid in DMSO, diluted 1:4, 50 ul diluted solution per well). Plates are covered with aluminum foil and incubated at 37° C. for 1-2 hours in an environment containing 5% CO₂. After the incubation the dye is emptied from the plates, and the cells are washed once with Krebs-Ringer HEPES (KRH) buffer (25 mM HEPES, 5 mM KCl, 0.96 mM NaH₂PO₄, 1 mM MgSO₄, 2 mM CaCl₂, 5 mM glucose, 1 mM probenecid, pH 7.4), and resuspended in KRH buffer.

Agonist (e.g., olvanil, capsaicin, or RTX)-induced calcium mobilization is monitored using either FLUOROSKAN ASCENT (Labsystems, Franklin, Mass.) or FLIPR (fluorometric imaging plate reader system, Molecular Devices, Sunnyvale, Calif.) instruments. Similarly, varying concentrations of the antagonists ruthenium red or capsazepine are added to cells concurrently with agonist (e.g., 25-50 nM capsaicin). For agonist-induced calcium responses, data obtained between 30 and 60 seconds after agonist application are used to generate the EC₅₀ values. KALEIDAGRAPH software (Synergy Software, Reading, Pa.) was utilized to fit the data to the equation:

y=a*(1/(1+(b/x)^(c))

to determine the EC₅₀ for the response. In this equation, y is the maximum fluorescence signal, x is the concentration of the agonist or antagonist, a is the E_(max), corresponds to the EC₅₀ or IC₅₀ value, and finally, c is the Hill coefficient.

Assay for Determination of Capsaicin Receptor Antagonist Effects

In order to measure the ability of a test compound to antagonize (inhibit) the response of cells expressing capsaicin receptors to capsaicin or other vanilloid agonist, the EC₅₀ of capsaicin is first determined.

An additional 20 ul of KRH buffer and 1 ul DMSO is added to each well of cells, prepared as described above. 100 ul capsaicin in KRH buffer is automatically transferred by the FLIPR instrument to each well. An 8-point concentration response curve, with final capsaicin concentrations of 1 nM to 3 uM, is used to determine capsaicin EC₅₀.

Test compounds are dissolved in DMSO, diluted in 20 ul KRH buffer so that the final concentration of test compounds in the assay well is between 1 uM and 5 uM, and added to cells prepared as described above. The 96 well plates containing prepared cells and test compounds are incubated in the dark, at room temperature for 0.5-6 hours. It is important that the incubation not continue beyond 6 hours. Just prior to determining the fluorescence response, 100 ul capsaicin in KRH buffer at twice the EC₅₀ concentration determined from the concentration response curve is automatically added by the FLIPR instrument to each well of the 96 well plate for a final sample volume of 200 ul and a final capsaicin concentration equal to the EC₅₀. The final concentration of test compounds in the assay wells is between 1 uM and 5 uM. Typically cells exposed to one EC₅₀ of capsaicin exhibit a fluorescence response of about 10,000 Relative Fluorescence Units. Antagonists of the capsaicin receptor decrease this response by about 20%, preferably by about 50%, and most preferably by at least 80% as compared to matched control. The concentration of antagonist required to provide a 50% decrease is the EC₅₀ for the antagonist (also referred to as the IC₅₀).

Equilibrium binding parameters may be determined as described in Example 10.

Assay for Determination of Capsaicin Receptor Agonist Effects

The ability of a compound to act as an agonist of the capsaicin receptor may be determined by measuring the fluorescence response of cells expressing capsaicin receptors, using the methods described above, in the absence of capsaicin, RTX, or other known capsaicin receptor agonists. Compounds that cause cells to exhibit fluorescence above background are capsaicin receptor agonists. Highly preferred compounds of the invention are antagonists that are essentially free of agonist activity as demonstrated by the absence of detectable agonist activity in such an assay at compound concentrations below 4 nM, more preferably at concentrations below 10 uM and most preferably at concentrations less than or equal to 100 uM.

Example 12 NPY Y5 Receptor Binding Assay

The following assay is a standard assay for NPY Y5 (neuropeptide Y receptor 5) receptor binding that may be used to determine the affinity of compounds for the NPY Y5 receptor. Expression of a recombinant human Y5 receptor in cultured cells and receptor binding assays using of membranes prepared from such cells has been described previously, e.g. in U.S. Pat. No. 5,602,024 at columns 17-20, U.S. Pat. No. 5,602,024 is hereby incorporated by reference for its teachings regarding a recombinant human Y5 receptor, expression of this receptor in cultured cells, and receptor binding assays using membranes prepared from such cells.

Cell Culture

Baculovirus-infected Sf9 cells expressing recombinant human NPY Y5 receptors are harvested at 48 hrs.

Membrane Preparation

Sf9 cell pellets are resuspended in lysis buffer (20 mM Tris-HCL, 5 mM EDTA, 0.5 ug/ml leupeptin, 2 ug/ml Aprotinin, 200 uM PMSF, pH 7.4) and homogenized using a POLYTRON homogenizer (setting 3 for 25-30 seconds). The homogenate was centrifuged (536×g/10 minutes/4° C.) to pellet the nuclei. The supernatant containing isolated membranes are decanted to a clean centrifuge tuber centrifuged (48,000×g/30 minutes, 40° C.) and resuspended in 30 ml homogenization buffer. This centrifugation and resuspension step is repeated twice. The final pellet is resuspended in ice cold Dulbecco's PBS containing 5 mM EDTA and stored in aliquots at −80° C. until needed. The protein concentration of the resulting membrane preparation is measured using the Bradford Protein assay, as described in Example 3. By this measure, a 1-liter culture of cells typically yields 100-125 mg of total membrane protein.

Thawed Sf9 membranes are washed with PBS and resuspended by Dounce homogenization (tight pestle) in binding buffer (50 mM Tris-HCl, 5 mM KCl, 120 mM NaCl, 2 mM CaCl₂₇ 0.1% BSA, pH 7.4).

For competition binding analysis, membranes (10-25 ug) in 150 ul binding buffer are added to polypropylene tubes or 96-well deepwell plates containing [¹²⁵I]PYY (porcine, NEN, Boston, Mass.)/GTP. Final concentration of [¹²⁵I]PYY is 30-35 pM/assay well; final concentration of GTP is 100 uM/well. Nonspecific binding is determined in the presence of 1 uM NPY (human, American Peptide Co., Sunnyvale, Calif.) and accounts for less than 10% of total binding. Test compounds at a concentration of 1-4 uM in 2 ul DMSO are added to the assay mixtures. Final assay volume is 250 ul For competition analysis test compounds are added at concentrations ranging from 10⁻¹² to 10⁻⁶ M. Typically 11 concentration points are collected per saturation binding curve. Following a 2-hour incubation at room temperature, the assay reactions are terminated by rapid vacuum filtration. Samples are filtered over presoaked (in polyethyleneimine for 2 hours prior to use) GF/C WHATMAN filters and rinsed 2 times with 5 mls cold binding buffer without BSA. Remaining bound radioactivity is quantified by gamma counting. Ki values may be determined by the method described in Example 10.

Preferred compounds of the invention exhibit 10-fold greater affinity for the capsaicin receptor than for the chimeric NPY Y5 receptor, more preferred compounds of the invention also exhibit 100-fold greater affinity for the capsaicin receptor than for the chimeric NPY Y5 receptor, and still more preferred compounds of the invention also exhibit 1000-fold greater affinity for the capsaicin receptor than for the chimeric NPY Y5 receptor. Most highly preferred compounds of the invention do not exhibit detectable binding at the NPY 5 receptor.

Example 13 Preparation of Radiolabeled Probe Compounds of the Invention

The compounds of the invention are prepared as radiolabeled probes by carrying out their synthesis using precursors comprising at least one atom that is a radioisotope. The radioisotope is preferably selected from of at least one of carbon (preferably ¹⁴C), hydrogen (preferably ³H), sulfur (preferably ³⁵S), or iodine (preferably ¹²⁵I). Such radiolabeled probes are conveniently synthesized by a radioisotope supplier specializing in custom synthesis of radiolabeled probe compounds. Such suppliers include Amersham Corporation, Arlington Heights, Ill.; Cambridge Isotope Laboratories, Inc. Andover, Mass.; SRI International, Menlo Park, Calif.; Wizard Laboratories, West Sacramento, Calif.; ChemSyn Laboratories, Lexena, Kans.; American Radiolabeled Chemicals, Inc., St. Louis, Mo.; and Moravek Biochemicals Inc., Brea, Calif.

Tritium labeled probe compounds are also conveniently prepared catalytically via platinum-catalyzed exchange in tritiated acetic acid, acid-catalyzed exchange in tritiated trifluoroacetic acid, or heterogeneous-catalyzed exchange with tritium gas. Such preparations are also conveniently carried out as a custom radiolabeling by any of the suppliers listed in the preceding paragraph using the compound of the invention as substrate. In addition, certain precursors may be subjected to tritium-halogen exchange with tritium gas, tritium gas reduction of unsaturated bonds, or reduction using sodium borotritide, as appropriate.

Examples 14a and 14b Preparation of Radiolabeled Aryl Piperazine Capsaicin Receptor Ligands Example 14a

example 14b

Example 15 Receptor Autoradiography

Receptor autoradiography (receptor mapping) is carried out in vitro as described by Kuhar in sections 8.1.1 to 8.1.9 of Current Protocols in Pharmacology (1998) John Wiley & Sons, New York, using radiolabeled compounds of the invention prepared as described in the preceding Example.

Example 16 Additional Aspects of Preferred Compounds of the Invention

The most preferred compounds of the invention are suitable for pharmaceutical use in treating human patients. Accordingly, such preferred compounds are non-toxic. They do not exhibit single or multiple dose acute or long-term toxicity, mutagenicity (e.g., as determined in a bacterial reverse mutation assay such as an Ames test), teratogenicity, tumorogenicity, or the like, and rarely trigger adverse effects (side effects) when administered at therapeutically effective dosages.

Preferably, administration of such preferred compounds of the invention at certain doses (i.e., doses yielding therapeutically effective in vivo concentrations or preferably doses of 0.01, 0.05. 0.1, 0.5, 1, 5, 10, 40, or 50 mg/kg administered parenterally or preferably orally) does not result in prolongation of heart QT intervals (i.e., as determined by electrocardiography, e.g., in guinea pigs, minipigs or dogs). When administered daily for 5 or preferably ten days, such doses of such preferred compounds also do not cause liver enlargement resulting in an increase of liver to body weight ratio of more than 100%, preferably not more than 75% and more preferably not more than 50% over matched controls in laboratory rodents (e.g., mice or rats). In another aspect such doses of such preferred compounds also preferably do not cause liver enlargement resulting in an increase of liver to body weight ratio of more than 50%, preferably not more than 25%, and more preferably not more than 10% over matched untreated controls in dogs or other non-rodent mammals.

In yet another aspect such doses of such preferred compounds also preferably do not promote the release of liver enzymes (e.g., ALT, LDH, or AST) from hepatocytes in vivo. Preferably such doses do not elevate serum levels of such enzymes by more than 100%, preferably not by more than 75% and more preferably not by more than 50% over matched untreated controls in vivo in laboratory rodents. Similarly, concentrations (in culture media or other such solutions that are contacted and incubated with cells in vitro equivalent to two, fold, preferably five-fold, and most preferably ten-fold the minimum in vivo therapeutic concentration do not cause release of any of such liver enzymes from hepatocytes in vitro into culture medium above baseline levels seen in media from untreated cells.

Because side effects are often due to undesirable receptor activation or antagonism, preferred compounds of the invention exert their receptor-modulatory effects with high selectivity. This means that they do not bind to certain other receptors (other than capsaicin receptors) with high affinity, but rather only bind to, activate, or inhibit the activity of such other receptors with affinity constants of greater than 100 nanomolar, preferably greater than 1 micromolar (uM), more preferably greater than 10 uM and most preferably greater than 100 uM. Such receptors preferably are selected from the group including ion channel receptors, including sodium ion channel receptors, neurotransmitter receptors such as alpha- and beta-adrenergic receptors, muscarinic receptors (particularly m1, m2, and m3 receptors), dopamine receptors, and metabotropic glutamate receptors; and also include histamine receptors and cytokine receptors, e.g., interleukin receptors, particularly IL-8 receptors. The group of other receptors to which preferred compounds do not bind with high affinity also includes GABA_(A) receptors, bioactive peptide receptors (including NPY and VIP receptors), neurokinin receptors, bradykinin receptors (e.g., BK1 receptors and BK2 receptors), and hormone receptors (including androgen receptors, thyrotropin releasing hormone receptors and melanocyte-concentrating hormone receptors).

Example 16a Sodium Ion Channel and Anti-Androgen Activity Criteria

Preferred compounds of the invention do not exhibit significant activity as sodium ion channel blockers, exhibiting less than 15 percent inhibition, and more preferably less than 10 percent inhibition, of sodium channel specific ligand (e.g., batrachotoxin, tetrodotoxin, or saxitoxin) binding when present at a concentration of 4 uM or less.

Preferred compounds of the invention do not exhibit significant androgen bioactivity, more preferably they do not exhibit significant androgen antagonist activity, e.g., in vivo, in a Hershberger assay, or in vitro, in an assay such as that described by Nellemann et al., Toxicology 2001, 163(1):29-38. Preferred compounds of the invention exhibit less than a 15% inhibition, more preferably less than a 10%, and most preferably less than 5% inhibition of androgen receptor activation in this in vitro assay when present at concentrations of 4 uM or less.

By significant activity is meant results varying from control at the p<0.1 level or more preferably at the p<0.05 level of significance as measured using a standard parametric assay of statistical significance such as a student's T test.

Example 16b Microsomal In Vitro Half-Life

Compound half-life values (t_(1/2) values) may be determined via the following standard liver microsomal half-life assay. Pooled Human liver microsomes are obtained from XenoTech LLC, 3800 Cambridge St., Kansas City, Kans. 66103 (catalog #H0610). Such liver microsomes may also be obtained, e.g., from In Vitro Technologies, Baltimore, Md. 21227, or from Tissue Transformation Technologies, Edison, N.J. 08837. Reactions are preformed as follows:

Reagents:

Phosphate buffer: 19 mL 0.1 M NaH₂PO, 81 mL 0.1 Na₂HPO₄, adjusted to pH 7.4 with H₃PO₄. Cofactor Mixture: 16.2 mg NADP, 45.4 mg Glucose-6-phosphate in 4 mL 100 mM MgCl₂. Glucose-6-phosphate dehydrogenase: 214.3 ul glucose-6-phosphate dehydrogenase suspension (Doehringer-Manheim catalog no. 0737224, distributed by Roche Molecular Biochemicals, Indianapolis, Ind. 46250) is diluted into 1285.7 ul distilled water. Starting Reaction Mixture: 3 mL CoFactor Mixture, 1.2 mL Glucose-6-phosphate dehydrogenase.

Reaction:

6 test reactions are prepared, each containing 25 ul microsomes, 5 ul of a 100 uM solution of test compound, and 399 ul 0.1 M phosphate buffer. A seventh reaction is prepared as a positive control containing 25 ul microsomes, 399 ul 0.1 M phosphate buffer, and 5 ul of a 100 uM solution of a compound with known metabolic properties (e.g. DIAZEPAM or CLOZEPINE). Reactions are preincubated at 39° C. for 10 minutes. 71 ul Starting Reaction Mixture is added to 5 of the 6 test reactions and to the positive control, 71 ul 100 mM MgCl₂ is added to the sixth test reaction, which is used as a negative control. At each time point (0, 1, 3, 5 and 10 minutes 75 ul of each reaction mix is pipetted into a well of a 96-well deep-well plate containing 75 ul ice-cold acetonitrile. Samples are vortexed and centrifuged 10 minutes at 3500 rpm (Sorval T 6000D centrifuge, H1000B rotor). 75 ul of supernatant from each reaction is transferred to a well of a 96-well plate containing 150 ul of a 0.5 uM solution of a compound with a known LCMS profile (internal standard) per well. LCMS analysis of each sample is carried out and the amount of unmetabolized test compound is measured as AUC, compound concentration vs time is plotted, and the t_(1/2) value of the test compound is extrapolated.

Preferred compounds of the invention exhibit in vitro t_(1/2) values of greater than 10 minutes and less than 4 hours. Most preferred compounds of the invention exhibit in vitro half-life values of between 30 minutes and 1 hour in human liver microsomes.

Example 16c MDCK Toxicity Assay

Compounds causing acute cytotoxicity will produce a substantial decrease of ATP production by Madin Darby canine kidney (MDCK) cells in the following assay. Preferred compounds of the invention will not.

MDCK cells, ATCC no. CCL-34 (American Type Culture Collection, Manassas, Va.) are maintained in sterile conditions following the instructions in the ATCC production information sheet. The PACKARD, (Meriden, Conn.) ATP-LITE-M Luminescent ATP detection kit, product no. 6016941, allows measurement ATP production in MDCK cells.

Prior to assay 1 ul of test compound or control sample is pipetted into PACKARD (Meriden, Conn.) clear bottom 96-well plates. Test compounds and control samples are diluted in DMSO to give final concentration in the assay of 10 micromolar, 100 micromolar, or 200 micromolar. Control samples are drug or other compounds having known toxicity properties.

Confluent MDCK cells are trypsinized, harvested, and diluted to a concentration of 0.1×10⁶ cells/ml with warm (37° C.) VITACELL Minimum Essential Medium Eagle (ATCC catalog #30-2003). 100 ul of cells in medium is pipetted into each of all but five wells of each 96-well plate. Warm medium without cells (100 ul) is pipetted in the remaining five wells of each plate to provide standard curve control wells. These wells, to which no cells are added, are used to determine the standard curve. The plates are then incubated at 37° C. under 95% O₂, 5% CO₂ for 2 hours with constant shaking. After incubation, 50 ul of mammalian cell lysis solution is added per well, the wells are covered with PACKARD TOPSEAL stickers, and plates are shaken at approximately 700 rpm on a suitable shaker for 2 minutes.

During the incubation, PACKARD ATP LITE-M reagents are allowed to equilibrate to room temperature. Once equilibrated the lyophilized substrate solution is reconstituted in 5.5 mls of substrate buffer solution (from kit). Lyophilized ATP standard solution is reconstituted in deionized water to give a 10 mM stock. For the five control wells, 10 ul of serially diluted PACKARD standard is added to each of the five standard curve control wells to yield a final concentration in each subsequent well of 200 nM, 100 nM, 50 nM, 25 nM, and 12.5 nM.

PACKARD substrate solution (50 ul) is added to all wells. Wells are covered with PACKARD TOPSEAL stickers, and plates are shaken at approximately 700 rpm on a suitable shaker for 2 minutes. A white PACKARD sticker is attached to the bottom of each plate and samples are dark adapted by wrapping plates in foil and placing in the dark for 10 minutes. Luminescence is then measured at 22° C. using a luminescence counter, e.g. PACKARD TOPCOUNT Microplate Scintillation and Luminescense Counter or TECAN SPECTRAFLUOR PLUS.

Luminescence values at each drug concentration are compared to the values computed from the standard curve for that concentration. Preferred test compounds exhibit luminescence values 80% or more of the standard, or preferably 90% or more of the standard, when a 10 micromolar (uM) concentration of the test compound is used. When a 100 uM concentration of the test compound is used, preferred test compounds exhibit luminescence values 50% or more of the standard, or more preferably 80% or more of the standard. Luminescence values less than 50% of the standard indicate a substantial decrease of ATP production.

Example 18 Animal Models for Determining Pain Relief and Sedation

The following experimental protocols can be used to determine the degree of pain relief and sedation provided by compounds of the invention, e.g., in comparison to pain relief and sedation provided by morphine or pain relief by ibuprofen.

Example 18a CFA Arthritis Model

Male SD rats are injected with 200 ml of CFA (0.1 mg heat killed and dried M. tuberculosis/ml) in the hind paw (100 ml on the dorsal and 100 ml on the plantar surface of the paw) essentially as described by Bertorelli R, Corradini L, Rafiq K, Tupper J, Calo G, Ongini E., Br J. Pharmacol. 1999 128(6):1252-8 and by Stein C, Millan M J, Herz A. Pharmacol Biochem Behav. 1988 31(2):455-51.

Rats are tested for thermal (as described by Hargreaves K, Dubner R, Brown F, Flores C, Joris J. Pain. 1988 32(11):77-88) and mechanical (as described by Tal M, Eliav E. Pain. 1996 March; 64(3):511-8) sensitivities on days 5, 6, and 7. Baseline data should be obtained for each animal prior to CFA injection.

On day 7, animals are treated orally with a compound of the invention, morphine or vehicle (2% vitamin E-TPGS) 1 hour prior to testing. Note: an oral dose of 5 mg/kg morphine has sedative effects.

Results are conveniently expressed as % of Maximum Potential Efficacy (MPE). 0% MPE is defined as analgesic effect of vehicle, 100% MPE is defined as an animal's return to baseline level of thermal or mechanical sensitivity.

Example 18b Mechanical Allodynia

This assay determines the effectiveness of compounds of Formulae I-IX and Formulae A-F in relieving at least one of the symptoms in an in vivo model of pain produced by spinal nerve ligation, namely mechanical allodynia.

Tactile allodynia is induced in rats using the procedures described by Bennet and Xie, Pain 1988, 33:87-107. Rats are anesthetized, e.g., with an intraperitoneal dose of pentobarbital sodium (65 mg/kg) with additional doses of anesthetic given as needed. The lateral aspect of each rat's hind limb is shaved and disinfected. Using aseptic technique, an incision is made on the lateral aspect of the hind limb at the mid-thigh level. The biceps femoris is bluntly dissected to expose the sciatic nerve. On one hind limb of each rat, four loosely tied ligatures are made around the sciatic nerve approximately 1-2 millimeters apart. On the other side of each rat, an identical dissection is performed except that the sciatic nerve is not ligated. The muscle is closed with a continuous suture pattern, and the skin is closed with wound clips or sutures.

Mechanical sensitivity is assessed using a procedure described by Chaplan et al. J. Neurosci. Methods 1994, 53:55-63. A series of Von Frey filaments of varying rigidity strength (typically eight filaments in the series) are applied to the plantar surface of the hind paw ipsilaterial to the ligations with just enough force to bend the filament. The filaments are held in this position for no more than three seconds or until a positive allodynic response is displayed by the rat. A positive allodynic response consists of lifting the affected paw followed immediately by licking or shaking of the paw. The order and frequency with which the individual filaments are applied are determined by using Dixon up-down method. Testing is initiated with the middle hair of the series with subsequent filaments being applied in consecutive fashion, ascending or descending, depending on whether a negative or positive response, respectively, is obtained with the initial filament.

Certain preferred compounds of Formulae I-IX and Formulae A-F are effective in reversing mechanical allodynia-like symptoms (i.e., rats treated with effective amounts of such compounds will require stimulation with a Von Frey filament of higher rigidity strength to provoke a positive allodynic response as compared to control untreated or vehicle treated rats) when tested by this method.

Example 18c Cold Allodynia

This assay determines the effectiveness of compounds in relieving one of the symptoms of neuropathic pain produced by unilateral mononeuropathy, namely cold allodynia.

Unilateral mononeuropathy is produced in rats using the Chronic Constriction Injury model performed essentially as described by Bennet and Xie, Pain 1989, 33:87-107. Rats are anesthetized. The lateral aspect of each rates hind limb is shaved and disinfected. Using aseptic technique, an incision is made on the lateral aspect of the hind limb at the mid-thigh level. The biceps femoris is bluntly dissected to expose the sciatic nerve. On one hind limb of each rat, four loosely tied ligatures are made around the sciatic nerve approximately 1-2 millimeters apart. On the other side of each rat, an identical dissection is performed except that the sciatic nerve is not ligated. The muscle is closed with a continuous suture pattern, and the skin is closed with wound clips or sutures.

Rats demonstrating unilateral mononeuropathy are assessed for acute and chronic cold allodynia sensitivity. Each rat is placed individually into a chamber with a metal plate about 6 cm from the bottom. This chamber is filled with ice water to a depth of about 2.5 cm above the metal plate, with the temperature of the bath maintained at about zero to four degrees C. throughout the experiment. A timer is started, and the rat's response latency is measured to the nearest tenth of a second. A “response” is defined as a rapid withdrawal of the ligated hindpaw completely out of the water while the animal is stationary and not pivoting. An exaggerated limp while the animal is walking is not scored as a response. Maximum immersion time is 20 seconds with a 20-minute interval between trials. The screening criteria are 1) the average of two trials is less than or equal to 13 seconds, and 2) there is consistency across the two trial scores. Animals are screened for hypersensitivity to cold on post-surgery days 4 through 10, and selected for inclusion in drug-response studies based on the criteria described above. The pre-dose screening values are used as the animal's baseline cold allodynia scores. For acute studies, the animals are tested for cold allodynia at 1, 3, and sometimes 5 hours post-dose.

Although this acute cold allodynia assay is generally less preferred for demonstrating efficacy of compounds of the invention, when tested in this assay, certain preferred compounds of Formulae I-IX and Formulae A-F demonstrate anti-allodynic effects (increases in response latency) at doses of less than 50 mg/kg.

Example 18d Mechanical Hyperalgesia

This assay determines the effectiveness of compounds in relieving one of the symptoms of neuropathic pain produced by unilateral mononeuropathy, namely mechanical hyperalgesia.

A chronic constriction injury is produced by loosely ligating the right common sciatic nerve as described by Bennet and Xie, Pain 1988, 33:87-107. The left common sciatic nerve is visualized, but not manipulated to produce sham conditions.

The rats having a chronic constriction injury are assessed for mechanical hyperalgesia to a pin-prick stimulus as described by Koch et al. Analgesia 1996, 2(3), 157-164. Rats are placed in individual compartments of a cage with a warmed, perforated metal floor. Hindpaw withdrawal duration is measured after a mild pinprick to the plantar surface of the ligated and sham hindpaws.

Preferred compounds of the invention produce a reduction of mechanical hyperalgesia (i.e., a reduction in the duration of hindpaw withdrawal) elicited by a pin-prick stimulus in rats with a chronic constriction injury at doses of 50 mg/kg or less when tested by this method.

Example 18e Thermal Hyperalgesia

This assay determines the effectiveness of compounds in relieving one of the symptoms of neuropathic pain produced by unilateral mononeuropathy, namely thermal hyperalgesia.

Rats having had surgery as described in Example 18d are assessed for thermal hyperalgesia sensitivity at least 10 days post-surgery. The rats are placed beneath inverted cages upon an elevated glass platform and a radiant heat source beneath the glass is aimed at the plantar hindpaw.

The duration of time before the hindpaw is withdrawn from the floor is measured to the nearest tenth of a second. The cutoff time for the heat stimulus is 20 seconds, and the light is calibrated such that this stimulus duration does not burn or blister the skin. Preferably about four latency measurements are taken for each hindpaw in each test session, alternating left and right hindpaws, with 5-minute intervals between tests. The times to withdrawal of each side are averaged and a difference score is obtained.

Preferred compounds of the invention produce an increase in the average time to withdrawal after oral administration of 50 mg/kg or less in this model.

Example 18f Sedation

Sedation may be determined using the method described by Fitzgerald et al., Toxicology 1988, 49(2-3)433-9. Preferred compounds of the invention do not produce reproducible or significant sedation at intravenous doses of less than 25 mg/kg (preferably less than 10 mg/kg) or at oral doses of less than mg/kg (preferably less than 50 mg/kg). 

1-237. (canceled) 238: A method of treating a mammal suffering from irritation due to exposure to tear gas, the method comprising administering to the mammal a therapeutic dose of a compound that is capsaicin receptor antagonist; wherein the therapeutic dose contains an amount of the compound that is effective to reduce severity of the irritation. 239: The method of claim 238 wherein the mammal is a human. 240: The method of claim 238 wherein the exposure is exposure of mucous membranes via eye contact or inhalation. 241: The method of claim 238 wherein the compound is administered in a pharmaceutical composition comprising a pharmaceutically acceptable carrier. 242: A method of treating a mammal suffering from inflammatory or bronchoconstriction symptoms resulting from exposure to tear gas, the method comprising administering to the mammal a therapeutic dose of a compound that is capsaicin receptor antagonist; wherein the therapeutic dose contains an amount of the compound that is effective to reduce severity of the inflammatory or bronchoconstriction symptoms. 243: The method of claim 242 wherein the mammal is a human. 244: The method of claim 242 wherein the mammal is suffering from inflammatory symptoms and the therapeutic dose contains an amount of the compound that is effective to reduce severity of the inflammatory symptoms. 245: The method of claim 244 wherein the compound is administered in a pharmaceutical composition comprising a pharmaceutically acceptable carrier. 246: The method of claim 242 wherein the mammal is suffering from bronchoconstriction symptoms and the therapeutic dose contains an amount of the compound that is effective to reduce severity of the bronchoconstriction symptoms. 247: The method of claim 246 wherein the compound is administered in a pharmaceutical composition comprising a pharmaceutically acceptable carrier. 